Joe's Firing System Expansiosn

Joe's Firing System Expansions

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In our last episode, directions and plans were given to construct an expandable electric firing system that could be as small as one slat of 20 cues or as large as six slats with a total of 120 cues. It was a 12 volt system that could fire up to three cues, on different slats, with one button push. If you have not read the first episode, you should read it before continuing with this episode.

Not wishing to leave well enough alone and to fulfill a desire to keep tweaking the firing system, here are three more optional expansions and two more variations to the expandable electric firing system. Although these expansions can be added to the firing system after it has been constructed, it will probably be easier if you add these when you first make it.

[1] Dual 12 or 24 Volt Firing System
[2] Fire Six cues with One Fire Button
[3] Continuous LED Status and LED Continuity Test Lights
[4] No Rotary Switch Panel
[5] No Push Button Panel

Note: all diagrams in this document are scaled drawings with each pixel
being 0.01" x 0.01".

Most pictures have been scaled down to fit on this page. Clicking on an image will bring up the full-size version.

[1] Dual 12 or 24 Volt Firing System
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This expansion will allow your firing system to use either 12 volts or 24 volts. A 24 volt system can fire more nichrome ignitors at the same time and it can fire then faster. It would also allow you to have longer slat cables and longer shooting wires.

All the electrical parts of the Expandable Firing System (alligator clips, wires, slat terminals, diodes, connectors and switches) can handle 24 volts with out difficulty, except the 12 volt lights. This expansion makes some minor changes so the lamps can handle 12 and 24 volts.

Materials

- three 150 (or 120-220) ohm, 1/2 watt (or more) resistors.
- three small twist-on wire connectors (gray)
- one additional 12 volt, 7 amp/20 hour battery (you should now have two).
- two alligator clips
- one piece short piece of 18 gage wire or thicker.

Making a 24 Volt Serial Battery

Strip a short piece of insulation from the ends of the wire. Attach an alligator clip to each end of the wire. The section "Constructing the Shooting Wire" from the Expandable Firing System describes how to attach the alligator clips to the wire. This short piece of wire with clips will be used to connect the two 12 volt batteries in series, so they produce twice the voltage (24) and twice the amperage (14).

Please examine the picture on the right. Place the two batteries side by side. Put one clip on the negative terminal of the first battery (1-)and the other clip on the positive terminal of the second battery (2+). The two remaining terminals 1+ and 2-, which are furthest from each other, are the terminals of the 24 volt serial battery. They are used to hook the heavy duty B+ and B- alligator clips from the firing panel.

Finding the Right Size Lamp Resistors

The resistors needed for this expansion will probably be somewhere between 120-220 ohms. This due to variations in resistors and 12 volt lights. The resistor will lower the amperage going to the light so it does not burn too brightly (or burn out) when you run 24 volts through it. But you don't want the resistance so high that the light is too dim when you run 12 volts through it, unless you are always going to use 24 volts. The resistor also prevents too much amperage from going to the cues when you push the fire button in test mode. If the resistance is not high enough when using 24 volts, the e-matches or igniters might fire in test mode.

Here are some tests to find the correct size resistor.

1) Touch the two wires of the light to the 1- and 1+ terminals of the first 12 volt battery and note how bright the light is using just 12 volts and no resistor.

2) Temporarily connect one wire of a resistor to a wire of the light. Touch the other resistor wire to 2- terminal and the other light wire to the 1+ terminal of the 24 volt serial battery. Note how bright the light is with 24 volts.

3) Do step 2 again, but touch the wires to the 1- and 1+ terminals of the first 12 volt battery. Notice how dim the light is with 12 volts. If you are only going to be using 24 volts, you can skip this step.

You want to brightness of the light in step 2, to be similar or slightly brighter than the brightness of the light in step 1. But you don't want the light to be too dim in step 3, unless you are always going to use 24 volts. If in step 2, the light is too bright, increase the resistance. If in step 3, the light is too dim, reduce the resistance. Retry the above steps again with the different resistance.

If you have a test meter, set it to test amps and add the meter serially to the resistor and lamp circuit and try the above steps again. Ideally, the amperage should be 60 milliamps (0.06 amps) or less. If you don't have a test meter, try adding a piece of igniter wire or an e-match serially to the resistor and lamp circuit and try the above steps again. If the igniter burns or the e-match fires, then you need a resistor with higher ohms.

Adding the Resistors

Flip over the firing panel and also look at the diagram to the right (click image to enlarge). The diagram shows the red and black wires of the firing panel. For clarity, the row and column cables are not shown, but it does show where they are attached with twist connectors (blue circles) to the rotary terminals and the push button terminals.

Observe toggle switch L1. Attach a resistor to the upper left terminal of toggle switch L1. Previously, the red wire was wrapped around the terminal. Since the resistor wire is smaller than the lamp wire, you may opt to wrap both the red wire and the resistor wire around the screw of the terminal and tighten the screw for a more secure connection. The other end of the resistor is attached to the wire of the lamp with a small gray twist connector. A resistor is also attached to the upper left terminals of switches C1 and R1. The picture below shows a close up of the L1 toggle switch. There is a 150 ohm resistor connected to the upper left terminal of L1. The other end of the resistor is attached to the light, using a gray connector.

You now can use one 12 volt battery or the 24 volt serial battery to run the electric firing system on 12 or 24 volts.

Circuit Discussion

The resistor reduces the amount of amps flowing into the lamp, which prevents it from burning out. It also reduces the amps flowing out to the cues during test mode. The amperage is low enough so it does not fire the igniters or e-matches. Most commercial e-matches will fire with 200 milliamps or more. The amount of amperage can be calculated using Ohm's law.

I = V / R

where I = amps, V = volts, and R = ohms.
So with 12 and 24 volts and a 150 ohm resistor:

I = 12 volts / 150 ohms = 0.08 amps = 80 ma
I = 24 volts / 150 ohms = 0.16 amps = 160 ma

The 150 ohm resistor reduces the amps to either 80 or 160 milliamps. But the lamp when it is burning during test mode, will probably add another 250-400 ohms depending on the lamp and the voltage. So let us assume it adds 250 ohms at 12 volts and 350 ohms at 24 volts:

I = 12 volts / (150 + 250) ohms = 0.03 amps = 30 milliamps.
I = 24 volts / (150 + 350) ohms = 0.048 amps = 48 milliamps.

[2] Fire Six cues with One Fire Button
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The Expandable Firing System was designed to fire a cue on three different slats at the same time. The idea behind this was that you could have one slat on the left side of the fire zone, one slat in the middle and one on the right side and fire a cue from each one. This lets you have three firework pieces firing at once, but spread out over your firing zone. But you may you may want to fire more cues at once, especially during the finale. This modification allows you to fire two cues from each slat, so you can fire a total of six cues from three slats at once. This expansion adds new rotary switch positions between positions A-B, C-D, E-F, G-H, I-J, and K-L that will activate the positions on either side of it. It also adds an off position between B-C, F-G and J-K.

For example, if you set the rotary to position to A, it activates row A. Pushing switch 3 will fire cue A3. If you set the rotary to position A-B between position A and B, it activates both rows A and B at the same time. Pushing switch 3 will fire both cues A3 and B3 at the same time. If rotary switches are set to A-B, E-F and I-J and switch 3 is pushed, cues A3, B3, E3, F3, I3 and J3 are fired at the same time.

If you do this expansion you should also expand the system to handle 24 volts as 12 volts may not be enough to fire six cues at once.

Materials

- 3 rotary switches with 7-12 positions.
- 12 3-amp, 50 volt or more diodes (1N5400-1N5408)

Adding New Rotary Switches

Flip over the firing panel and also look at this diagram. The diagram shows the red and black wires of the firing panel. For clarity, the row and column cables are not shown, but it does show where they are attached with twist connectors (blue circles) to the rotary terminals and the push button terminals. The original 4 position rotary switches have been replaced with 12 position rotary switches. Only a seven position rotary switch is needed, but 12 position rotary switches are more common. The extra positions can be used for off positions. Examine rotary L3. The row terminals are at positions 1, 3, 9 and 11 o'clock positions. The other positions are left open. There is one open position between each of the row positions. Add the new rotary switches, but don't connect the
row wires yet.

Adding Diodes

After the L3, C3 and R3 rotary switches have been added but before the row wires are attached, connect two diodes to the terminals between the A-B terminals. Usually rotary switches have a terminal with a hole in it. The diode wires can be slid into this hole and twisted around the terminal. This eliminates the need for soldering. If the hole is too small, use an awl to make it a bit bigger, so the diode wires just fit. Important: the end of the diode WITHOUT the black band (anode) is attached to the A-B terminal. Take one of the diodes and attach the end of the diode WITH the black band (cathode) to the A terminal with the row A wire. Take the other diode and attach the cathode end to the B terminal with the row B wire. This picture shows a close up of rotary L3 with the row wires and diodes attached. Finish the process for terminal C-D. Repeat the process for terminals E-F, G-H on rotary switch C3 and terminals I-J, K-L on rotary switch R3. Click the picture to

Discussion and Testing Rotary Terminals

As mentioned in the "Expandable Firing System" diodes form a one way electrical wire flowing from the anode to the cathode (black band side). If the rotary switch is set to position A, power can flow to the row A wire. But the diode prevents the power from going to terminal A-B and then to terminal B to the row B wire. Likewise if the rotary switch is set to position B, the power can flow to the row B wire, but not terminal A-B and then terminal A. But if the rotary is set to terminal A-B, the power can flow both to terminal A and B through the diodes. Then power can flow to the row A and B wires at the same time. This works the same way for all the other rotary terminals.

To test the circuit, turn off R1 and C1. Turn L1 to TEST position. Attach the battery to B+ and B-. Move the rotary switch to position A. Touch a test wire from B- to terminal A. The L2 light should go on. Touch the test wire from B- to the terminal A-B and then to terminal B. The light should be off for both touches. Move the rotary to position A-B. Touch the test wire from B- to the terminals A, A-B and B. The light L2 should be on for all three touches. Now move the rotary switch position B and touch the test wire from B- to terminals B (on), A-B (off) and A (off). Repeat these tests for terminals C, C-D and D. Turn off L1 and turn
C1 to TEST position. Do the tests for all the terminals on C3. Turn off C1 and turn R1 to TEST position. Do the test for all the terminals on R3. When done, turn off R1 and remove the battery.

In this expansion, I left terminals B-C, F-G and K-J as off positions. If desired, you could run diodes from these terminals to the terminals on either side of them. This would require six more diodes. It might be a bit tricky to have three wires attach to some terminals without soldering. I prefer an off position for two reasons. One is to have an off position so it makes it easier to use the LED continuity lights in the next expansion. Also, I find that if I fire rows A and B together, there are no cues left on row B to fire with row C. It then makes more sense to fire rows C and D together.

[3] Continuous LED Status and LED Continuity Test Lights
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At the right is a picture of the firing panel with this expansion and the previous two expansions. This expansion adds green LED status lights by each of the rows on the rotary switches. The status LED will turn on when the rotary switch is turned to that row and the toggle switch for the rotary is either in test or on position. It is very obvious from the picture that rows A, E, F and I are active. It is a useful visual aid during set up and show to indicate which rows are turned on and active. The picture also shows the previous expansion. Notice the center rotary switch is set to the E-F position and both the E and F status lights are on.

This expansion also adds red LED continuity test lights to each of the push buttons. The LED continuity lights continuously show if the cues have continuity or not when the toggle switch is in either test or on position. During the show they can indicate if a cue has been fired or not. These LEDs are useful for show set up and display. They add another way to show continuity on the cues, in addition to the test lamp.

Here is an example how these LEDs and test lamps would be used during setup and display. Say you need to see the continuity of cue A1. All the toggle switches are set to test mode. Turn the left rotary switch to A and turn the other rotary switches to the off positions. Only the green status light above the "A" will be lit to indicate that row is active. The red LED above "1" will be on if there is continuity or off if there isn't. As soon as there is continuity it will turn on. If continuity is broken it will turn off again. All the red LEDs will show the continuity of cues A0-A9. A0-A4 are on first left slat and A5-A9 are on the second left slat. So you can see all ten cues for row A at once, which speeds up testing. You can also push the "1" fire button and the test lamp above the left rotary would light. The cue would NOT fire because it is in test mode. This is a safety feature to prevent accidental firing.

If you need to check a cue in row B, just move the rotary switch to position B. The green LED will show that row B is active and all red LEDs will show the continuity cues in row B. To test any cue in row E, turn the left rotary switch to off and then turn the center rotary switch to row E. This is why it is useful to an off position on all the rotary switches, otherwise you would have use the toggle switch to switch between test and off mode. That process would be a bit more error prone as you might pull the toggle switch to on instead of off.

Just before the show starts, you might position rotary switches to A, E and I. The green LEDs will show that row A, E and I are active. At this point, the "0" LED would be lit if any or all of A0, E0 or I0 have continuity and it would be off if only if none of them have continuity. This would be true for LEDs "1"-"9" also. This is not real useful test. But now you can push the "0" push button and the three test lamps will be lit or unlit depending on the continuity of A0, E0 and I0. By pushing
all the push buttons and changing the rows, you can quickly test all your cues in the same order that you will be firing them, but three at a time. This tests cues across slats, instead of all the cues in the same row.

Now it is show time. The toggle switches are set to on (arm) mode. Rows A, E and I are active. Pushing button "0" will fire cues A0, E0 and I0. If all the cues fire, when you release the button the red "0" LED will be off. This is VERY useful. You can immediately see if all the cues fired and you can push the button again if the LED is still lit. If it is still lit, you can flip the toggle switches to test mode and push the button again to see which ones misfired. If all the cues fired, you have a visual indication that the "0" button has been fired because its LED is off. The next button to fire is "1" because its LED is on. The red LEDs also help you find the push buttons in the dark. Once all the cues for these rows are fired, all the red LED lights will be off and this indicates it is time to switch the rotary switches, to other rows. The green LEDs help you find the rotary switches in the dark.

Materials

- 12 5mm Green LEDs, 10-30 milli-amps, 1.5-3.0 volts.
- 10 5mm Red LEDs, 10-30 milli-amps, 1.5-3.0 volts.
- 22 LED holders or one Christmas tree mini-light string with replaceable light bulbs.
- Colored marker or Typing Correction Fluid
- 5 medium twist-on wire connectors (blue).
- 5 1.2K (2200)-3.3K (3300) ohm resistors, 1/2 watt or larger.
- wood glue

LEDs

LEDs, or Light Emitting Diodes, are diodes that give off light when current flows from the positive side (anode) to the negative side (cathode). It stops the flow of power and gives off no light when the power tries to flow the other direction. To the right is a diagram of a LED. The long wire is the positive side (anode) and the side with the short wire and flat side is the negative side (cathode). LEDs come in many varieties and capabilities. Any 5 mm LED that has voltage between 1.5 and 3 and amps between 10 and 30 milli-amps will work fine.

The LEDs have no filaments that can burn out so they last longer than lights. They also require considerable less power than a light. A high ohm resistor is used to protect the LEDs from receiving too much power and burning out. Warning: If you touch the leads of a LED directly to the 12 volt, 7 amp battery it will be ruined. It will either burn out immediately or it will crack or it will always burn dimly thereafter.

Finding the Right Size LED Resistor

LEDs usually have a "typical" milliamp value and a "maximum" milliamp value. If the amps exceed the maximum value then it will probably burn out. The trick is to find a resistor that makes the LED light near or below the typical value. Ohms law helps us figure out the correct resistance for the resistor. Let us assume you will be using both 12 and 24 volts and the LEDs have a 10 milliamp typical value and a 15 milliamp maximum value. So you want about 10 milli-amps flowing through the LED at 24 volts.

R = V / I = 24 volts / 0.01 amps = 2400 ohms or 2.4K ohms

You are more likely to find a 2.2K resistor than a 2.4K resistor so you use a 2.2K resistor to calculate milliamps for 12 and 24 volts. Also note that the 150 ohm resistor by the test lamp, is added to circuit when it is in test mode. So this adds another 150 ohms for a total of 2350 ohms.

I = V / R = 12 volts / 2350 ohms = 0.0055 amps or 5.1 ma
I = V / R = 24 volts / 2350 ohms = 0.0102 amps or 10.2 ma

The LEDS will burn a little dimmer on 12 volts. Note that this is also the amperage that will constantly flow out to the cues in test mode.

You may want to lower the milliamps to dim the LEDs (and use less power) or raise it some to brighten the LEDs. You can test the brightness of the LEDs with different resistors by using these tests.

1) Temporarily connect one wire of the resistor to the long wire of the LED (anode). Touch the other resistor wire to the 1+ terminal and the cathode wire to the 1- terminal of the first 12 volt battery. Note the brightness of the LED at 12 volts.

2) Do step 1 again, but touch the resistor wire to the 1+ terminal and the cathode wire to the 2- terminal of the 24 volt serial battery. Note the brightness of the LED at 24 volts.

You want don't want the LED in step 1 too dim and you don't LED in step 2 too bright. Increase the resistance to dim the LED or decrease resistance to brighten the LED.

Make or Buy LED Holders

You need to have LED holders. They are small plastic or metal devices that hold the LED. The LED holders then screw into a hole in the top of the firing panel. The LED is then placed into the holder. The trouble with this is that you then have two non-insulated, thin and short LED leads you have to hook up. You would probably have to solder them. If you don't mind soldering, it is not a problem, but it does makes it more difficult to modify your firing panel at a later time or replace a LED if needed.

You can also buy complete LED assemblies. These are a LED with a LED holder and there are insulated lead wires attached to the LED holder that you can use to connect it to the circuits without soldering. The problem is these LED assemblies can be expensive. This section describes how to make LED holders with insulated lead wires out of a string of Christmas mini-lights. If you do not wish to make your own holders, skip to the next section.

Find a cheap set of Christmas mini-lights with 25-35 lights, like the ones in the picture. They should be the type with the replaceable (pull out) bulbs. The bulb socket and bulb base should be plastic. If the socket is bigger at the top than at the bottom, that is even better. Snip off the electric plug from the end. You should have two wires that go to the string of lights. They are usually twisted together so it looks like there are three wires in the chain. If you untwist all the wires you will end up with one long wire with the mini-lights connected serially.

Once the mini-light string is untwisted it should look like this diagram. You want to cut the wire half-way between each of the lights so you will have the longest possible lead wires for each light. Note, sometimes the first light has three wires or some sockets are bigger to hold a fuse light. You can just throw these away. Strip about 5/16" of the insulation off each lead of each light. Inside each lead will be very thin strands of wire. Twist those very thin wires together to make a thicker "twisted" wire. This will be much easier to use with the twist connectors and screw terminals than the separate thin wires.

You are now going to replace each of the light bulbs with LEDs. In this diagram, you will see the light bulb is attached to a small base. The base and bulb pull out of the socket. If needed, wedge a small screw driver between the base and the base holder and turn the screw driver to force the base up. At the bottom of the base are two small holes where the bulb wires come through and are bent up against the base. Straighten the wires and you should be able to easily remove the bulb from its base. Now take a LED and stick the lead wires into the base and through each of the two holes. Use a needle nose pliers and firmly bend
each lead up on either side of the base, where the bulb wires were. Clip off excess wire from the leads. If done properly, the lead wires will hold the LED in place and it will not wiggle or move. Stick the LED and base into the its LED holder, which was formerly the light socket. You now have a LED and LED holder with long insulated lead wires.

There is now one small problem. You don't know which leads are the anode (+) and the cathode (-). As we did in the previous section, touch one LED resistor wire to the 1+ terminal of the first battery. Touch the other LED resistor wire to one of leads of the LED holder. Touch the other lead of LED holder to the 1- terminal of the battery. If the LED lights, mark the lead that is touching the 1- terminal with a colored marker or white correction fluid. This is the cathode (-) side. If the LED did not light flip the leads, retry and it should light. Mark the lead touching the 1- terminal. If it still does not light, pull out the LED from the LED holder and check the LED leads. Make sure the LED is firmly in the LED holder.

Adding LEDS to the Firing Panel

It is now time to drill holes for the LEDs. The size of the holes will depend on the size of your LED holders. You want them to fit snuggly in the holes. In this diagram (click to enlarge), you will see where the holes are to be drilled. LED holes B, C, F, G, J, K are drilled 4.2" from the back edge and 3.25", 4.75", 7.25", 8.75", 11.25" and 12.75" from the left edge. Warning, if you are expanding an existing panel, make sure the wires in the panel are out of the way of the drill bit. Otherwise, you will chew up your wires and have wires wrapped around your drill bit. LED holes A, D, E, H, I, L are drilled 5.5" from the back edge and 2.5", 5.5", 6.5", 9.5", 10.5" and 13.5" from the left edge. LED holes 0-9 are drilled 7" from the back edge and 1.25", 2.75", 4.25", 5.75", 7.25", 8.75", 10.25", 11.75", 13.25" and 14.75" from the left edge (one inch above the push button switches).

Flip the panel over from left to right so the bottom is in view. Examine this diagram on the left. Warning: since this view is of the bottom of the box, all the holes are reversed from left to right. If you bought LED holders screw them into the holes. The green LEDs go in A-L holes and the red LEDs go in the 0-9 holes. Notice that you want all the cathodes (-) to be up and the anodes (+) to be down.

If you made your own LED holders, put some wood glue in the hole and some on the holder. Wait for the glue to get a little tacky and then insert the LED holder into the hole. Make sure the edge of the holder sticks out from the panel top by about 1/16". This will allow you the LED base to stick out far enough so it can be removed from the holder and replaced, if needed. It will also leave you some room to paint the top of the panel. Make sure the cathodes (-) are up and the anodes (+) are down. Let the glue dry overnight.

Attaching Green Status LEDs to Rotary Switches

This diagram shows how to hook up the green status LEDs to the rotary switches. First attach a LED resistor to the upper right terminal of toggle switch L1. This resistor will be used with the green LEDs by rotary switch L3. Attach a twist connector to the other end of the resistor and bring the other end down near L3. Take the cathodes of LEDs A-D and put them into the twist connector also. Below is a picture of a 2.2k resistor attached to the upper right terminal of switch L1. The other end of the resistor goes into the blue twist connector with the cathodes. The wiring may get a bit crowded. You may have to move the row slat cables out of the way. Make sure the lighter LED leads are always under the heavier row wires and the red wires.

To test your connections, attach the battery to B+ and B- and turn L1 to test mode. Run a test wire from the common terminal of the rotary switch L3 to each of the anode end of the LEDs. The LEDs should light up and the test lamp L2 should not light. Disconnect the battery. Repeat this process for toggle switch C1, LEDs E-H and rotary switch C3. Then do it for R1, LEDs I-L and R3.

The next step is to attach the green LED anodes to the appropriate row wire. Look closely at rotary switch L3. Attach the anode of LED A to the twist connector that is connected to terminal A. Row A wires are also attached to this connector. Repeat this for LEDs B-D also. To test this circuit, attach the battery to B+ and B- and put the toggle switch L1 into test mode. The test light L2 should not light. Move the rotary switch to each position and the appropriate LED light should light. Now move the toggle switch L1 to "on" mode. The light L2 should light and the LEDs should light when you move the rotary switch. Disconnect the battery. Repeat this process for LEDs E-H and then for LEDs I-L.

Discussion of Green Status LED Circuit

When L1 is turned to test mode, the positive power flows from B+ to the upper left terminal of L1. This then flows through light L2 to the lower left terminal of L1 and then out from the center left terminal. This power then flows to the common terminal of rotary switch L3. Assuming the rotary is set to position A, the power flows to the A twist connector. The power will continue on to the row A wires (and out to the cues) and to the A LED. Since it is positive power, it goes through the LED and lights it. The power continues out the cathode and to the resistor that is attached to the upper right terminal of L1. The resistor prevents the LED from burning out. The power continues on to B- to complete the circuit. Note that, the high ohm LED resistor provides enough resistance that there is
not enough power for the L2 to light, but L2 still lets power through the circuit. Note, the L2 light may burn very dimly in test mode with 24 volts. In this case, you may want to increase ohms of either the lamp or LED resistor.

When L1 is turned to on mode, the positive power flows from B+ to the upper left terminal of L1. It then goes to the center left terminal and out to the common terminal of rotary L3. This goes out to row A. It will also go through LED A and back to the upper right terminal of L3 as it did when in test mode. The power from upper left terminal also flows through the L2 light. From there it goes to the right center terminal of L1 and then to the upper right terminal which then completes the circuit. L2 lights indicating on or armed mode. Note that L2 lights because the high ohm LED resistor is circumvented. Also note that the power will not flow back through the resistor and LED A because the LED will not let the power flow that way.

Attaching Red Continuity LEDs to Fire Buttons

This diagram shows how to hook up the red continuity status LEDs to the fire buttons. This will be easier than the attaching the green status lights as you will have more room to work. Attach a LED resistor to the lower terminal of push button 2. Stretch the other end of the resistor between push buttons 2 and 1 towards the back of the panel. Take the five cathodes (-) from LEDs 0-4 and the resistor wire and connect then with a twist connector. Attach the anode ends to the matching upper terminals of the push buttons 0-4. To test this circuit, attach the battery to B+ and B-. Turn L1 to test mode. Light L2 should be off. Touch one end of a test wire to B+ and the other end to the upper terminals of push buttons 0-4. The LED for each fire button should light. Turn the L1 switch to on. Light L2 should be on. Touch the test wire to each of the upper terminals of push buttons 0-4 and the LED for each push button should light. Disconnect the battery. Next do this same process for push buttons 5-9. The LED resistor should be attached to lower terminal of push button 7. The picture below is close up of push buttons 5-9. There is a 2.2K resistor attached to push button 7 and to all the cathodes of LEDs 5-9.

Discussion of Continuity LED Circuit

If toggle switch is in test mode or arm mode, power will be flowing out to the row wires via the L1 switch and rotary switch L3. This was discussed above in "Discussion of Green Status LED circuit" section. If there is continuity on the cue, the power will come back via the column wires attached to push buttons 0-9. Normally the fire buttons keep the circuit open until they are pushed. But now the power flows through the red continuity LEDs, through the resistor and back to the B- terminal which completes the circuit. The resistor keeps the LED from burning out and it also keeps the flow of power so low that the igniter or e-match do not fire. Note that if the cue does not have continuity, the LED will not light.

If the L1 toggle switch is in arm mode and a push button is fired, the LED and resistor are taken out of the circuit and full power flows through the igniter or e-match and fires it. Note that the LED and its resistor prevents power from flowing backward from the lower terminal back to the upper terminal. If L1 toggle is in test mode and a push button is fired, the power flows first through the lamp resistor and lamp and then to the cue. The power is reduced enough to prevent the igniter or e-match from firing, but it is still high enough to light the lamp which indicates continuity. Note, if the lamp burns dimly with 24 volts during test mode, you may want to increase the resistance of the LED or lamp resistors.

Project Complete

Here are some pictures of the completed project. The one on the left shows the inside of the firing panel. It has all three the expansions. You will note that it is a "rats nest" of wires, especially around the rotary switches. If you add the expansions after the Expandable Firing System is built, it feels like you are trying to fit 10 lbs of stuff into a 5 lb box. A little bigger box might help. The one on the right is of another "rats nest". You now know two reasons why I use the alias "RatMan". The third reason is that there was an early Chinese ground firework called a "ground rat". My shows only use "ground" fireworks or "Safe and Sane", so I am a "rat man".

The picture on the right shows the firing panel in dim light. It is in arm mode (test light is on), rows A, E, F and I are ready to fire. The cues 0-9 are all have continuity and are ready to fire. The LEDs and lamps give you a lot of useful information. The picture on the left is of the firing panel in complete darkness with no power. All the fire buttons, rotary switches, toggle switches, 0-9 and A-L are have 8 hour, Ultra Green "Glow in dark" paint around them. It makes it easy to see the panel in the dark.

[4] No Rotary Switch Panel
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This is variation of the Expandable Firing System. In this system, two SPDT toggle switches replace each rotary switch. Some people had asked me how to make the firing system without using rotary switches as rotary switches can be hard to obtain. Also some people prefer using toggle switches instead of rotary switches.

Another advantage of this system is that you can activate two rows from each slat at once which allows for firing six cues with one button. If you plan to fire more than 3 cues at once, you should also expand the system to handle 24 volts. One disadvantage of this system is sometimes you have to turn off a row as well as turn on a different row when you change rows. This is not the case with rotary switches.

The previously mentioned expansions could also be added to this variation so the panel could handle 24 volts and have LED status and LED continuity lights.

Materials (replaces three rotary switches)

- 6 SPDT, center off, toggle switches, 10A at 125VAC 1/2" hole
- 18 gage red wire

Drill the SPDT switch holes in the top of the firing panel as in this diagram. Measure 4" from the left edge and 4.5" from the back edge and drill a 1/2" hole for the A-B SPDT switch. Drill another hole 1" below it (4.0",5.5") for the C-D SPDT switch. The E-F switch will be at (8",4.5"), the G-H switch at (8",5.5"), the I-J switch at (12",4.5") and the K-L switch at (12",5.5").

Flip the box over from left to right, so the bottom of the box is in view. Look at the diagram on the left. Warning: since this view is of the bottom of the box, all the holes are reversed from left to right. Screw the SPDT switches into the A-B, C-D, E-F, G-H, I-J and K-L holes. Note that the toggle switch will be going left and right, not up and down like the L1, C1, and R1 toggle switches.

Attach a red wire from the center left terminal of L1 to the common terminal of switch A-B and switch C-D. This was the wire that ran to the common terminal of the rotary switch in the previous firing panel. Repeat the process for switch C1 and switches E-F and G-H. Finally repeat the process for switch R1 and switches I-J and K-L.

Please note that toggle switches have some confusing properties. When the toggle switch is straight up, both the left and right terminals are open. No electricity can flow to the terminals. When the toggle is switched to the left, the center and right terminals are closed and the left is open. So electricity can flow from the center terminal to the right terminal. When the toggle is switched to the right, the center and left terminals are closed and the right is open. Electricity can flow from the center terminal to the left terminal. That is why the terminals may seem like they are wired backwards. For example, terminal A is on the left from the bottom view. When you flip the panel over, you switch the A-B toggle to the left to activate row A, even though is seems like it should be switched to the right.

Discussion and Testing Circuits

Now that some of the panel is wired, examine circuits L1-L3 to see how they work and to test them. Cue A0 will be fired. SPDT A-B is switched to the left (row A is active) and SPDT C-D is set to the off position. The L3 DPDT is switched off (centered). Attach the battery to B+ and B-. Use a piece of test wire, with some insulation stripped of the end and touch one end to terminal A and the other end to upper terminal of switch 0.

Power comes from B+ over to the top left terminal of L1. It also goes through the light to the lower left terminal and then to the center right terminal. Since the switch is off, power can not get to the center left terminal, so the whole circuit is open. While holding the test wire between terminal A and the upper terminal of switch 0, push switch 0 and nothing happens.

Push switch L1 up to put it in test mode. There is now contact between each center terminal and bottom terminal (but not between each center terminal and top terminal). Power comes to the left top terminal. It can't flow between the top and center terminal. But it flows to the light to the lower left terminal. Because there is contact, it will flow from the left bottom terminal to the center left terminal. From there it goes to L3 and out to terminal A. The test wire mimics an igniter on cue A0. Terminal A will be attached (it isn't yet) to row A of the left slat via the row A wire that goes out through hole L4. Power will go through an igniter and come back through the column 0 wire that will (it isn't yet) go through hole L4 to the top terminal of switch 0. This will then go back to B- when switch 0 is pushed, which makes a closed circuit. Push switch 0. Light L2 should light up.

Now turn try running the test wire to other push button switches and push the button. L2 should light up. Switch A-B to B position and try testing B with the push button switches. Turn off switch A-B and try switch C-D with the push buttons.

If you push L1 down, it is in armed mode and the L2 light should go on and stay on. Don't push any buttons. Switch the L1 switch to off.

Try the above process with C1 and the E-F and G-H switches and with L1 and the I-J and K-L switches.

REMOVE BATTERY when done.

Use the directions from the Expandable Firing System to finish this panel. Just remember that each of the two pair of toggle switches L3, C3 and R3 are substitutions for rotary switches L3, C3 and R3. You should continue with the section labeled "Adding the First Three Connectors and Slat Cables".

[5] No Push Button Panel
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This is variation of the Expandable Firing System. In this, five SPDT momentary toggle switches replace the ten more expensive push buttons. Some people had asked me how to make the firing system without using push buttons as push buttons can be expensive and sometimes are hard to obtain. Also some people prefer using momentary toggle switches instead of push buttons.

Another advantage of this system is that it is much easier to fire all six slats. In the Expandable Firing System, if you wanted to fire a cues A0, E0, I0 from the first three slats, followed by A5, E5 and I5 from the second three slats, you would have to push "0" and the reach over and push "5". In this variation, you push the momentary toggle switches forward to fire switches 0-4 and pull momentary switches backward to fire switches 5-9. So to fire A0, E0, I0 A5, E5 and I5 you push forward on the toggle switch and then pull back on the same switch.

The previous expansions can be added to this variation. Also this variation could be combined with the previous variation to make a firing panel that uses all toggle switches and momentary toggle switches.

Materials

- 5 SPDT momentary switches

Examine this diagram [ExPanel16.gif]. This example shows the red and black wires and where the slat cables would be connected, but not the slat cables. The diagram also has the 24 volt and LED expansions already added.

Note that the SPDT switches are using the same holes that push buttons 0-4 used. There is now empty space where the push buttons 5-9 use to be in other diagrams.

The B- black wire is attached the common terminal of the five momentary SPDT switches. The column wires are attached to the terminals of the SPDT switches. Examine the 0-5 SPDT switch on the far right. Pushing the toggle switch up, will close the common terminal and the lower terminal. This will allow switch "0" to fire. Pulling the toggle switch down will close the common terminal and the upper terminal. This will allow switch "5" to fire.