# Continuity test circuit voltage

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Handeman, thanks...that's pretty much what I was seeking...a way to learn about how to figure it out. I understand that not all answers can be taught in a forum...but sometimes a map of how to get there helps immensely! As said, I can solder wires together, put switches in a box, and send 12 v down a wire....is the continuity circuit needed, no. But I do like to have the knowledge of how to do it...rsbhunter Again, thank you.

You guys are awesome !!!!....I realize that alot of people want the "easy button". While I was taught to work smart and not hard (if possible) , I've never shied away from researching and learning what was needed to accomplish my goal. As I stated, I’ll be 69 years old next month...I am building a launch pad, 8' 1010 rail, and now a launch controller. I will do both of these ONCE in my life. I don't need to know the modulus strength of 2" compared to 2.5" square .065 thick steel square tubing to build a launch pad. I also don't need to know ohms law to put 12 volt 8-10 amps through a 30' ( or 50') length of wire. I appreciate the help, I know some of the 20,30 and older guys get into every facet of Rocketry. At that age, I would have also...but that ship has sailed...rsbhunter

You guys are awesome !!!!....I realize that alot of people want the "easy button". While I was taught to work smart and not hard (if possible) , I've never shied away from researching and learning what was needed to accomplish my goal. As I stated, I’ll be 69 years old next month...I am building a launch pad, 8' 1010 rail, and now a launch controller. I will do both of these ONCE in my life. I don't need to know the modulus strength of 2" compared to 2.5" square .065 thick steel square tubing to build a launch pad. I also don't need to know ohms law to put 12 volt 8-10 amps through a 30' ( or 50') length of wire. I appreciate the help, I know some of the 20,30 and older guys get into every facet of Rocketry. At that age, I would have also...but that ship has sailed...rsbhunter
I'll be 69 on May 6th. I don't have much patience anymore trying to learn anything new!!

I still love to learn, but I know what you mean...I won't put up with being force fed! People need to realize, the older I get, the less "life sentence" is a threat!

Here is a little simpler way to understand a simple launch controller. In place of light bulb can add a momentary push button switch and a piezo buzzer. Can add momentary switch before the light bulb also, so not constantly on. https://www.robotroom.com/Model-Rocket-Launch-Controller.html

View attachment 642213

This circuit is a BAD example of a launch controller.

It is a representation of the ESTES electron beam controller. The circuit TEST current limited by the SPECIFIC bulb supplied with the ESTES controller and is suitable ONLY for estes MODEL ROCKET IGNITERS. The reason for this is that the ESTES igniters are very INSENSITIVE and you can put a lot of current through them without them firing. You cannot do that with other igniters or e-matches.
The circuit presented does not show the functionality of the SAFETY SWITCH operation activated by the conductive steel pin supplied by ESTES with the controller.
Additionally, the really thin wire that ESTES supplies as part of the controller to connect from it to the rocket motor with the igniter fitted act as a resistor and current limit the draw from the AA battery cells.
The circuit looks simple when drawn out simplisticly here, but is not.

ESTES igniters are ONLY suitable for ESTES motors or their equivilant.

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This circuit is a BAD example of a launch controller.

It is a representation of the ESTES electron beam controller. The circuit TEST current limited by the SPECIFIC bulb supplied with the ESTES controller and is suitable ONLY for estes MODEL ROCKET IGNITERS. The reason for this is that the ESTES igniters are very INSENSITIVE and you can put a lot of current through them without them firing. You cannot do that with other igniters or e-matches.
The circuit presented does not show the functionality of the SAFETY SWITCH operation activated by the conductive steel pin supplied by ESTES with the controller.
Additionally, the really thin wire that ESTES supplies as part of the controller to connect from it to the rocket motor with the igniter fitted act as a resistor and current limit the draw from the AA battery cells.
The circuit looks simple when drawn out simplisticly here, but is not.

ESTES igniters are ONLY suitable for ESTES motors or their equivilant.
Oz, I know you mean well, but I'm not trying to detonate plastique explosive....I understand you have good intentions, but you have no knowledge of my knowledge of anything. Before you assume something, why don't you take a minute and realize that everybody has different approaches to things. As far as pryo stuff, I actually have a very great knowledge of the field. So, if I ever have the need to learn how to detonate something, and i don't know how to, I will consult you. Thanks, rsbhunter

Oz, I know you mean well, but I'm not trying to detonate plastique explosive....I understand you have good intentions, but you have no knowledge of my knowledge of anything. Before you assume something, why don't you take a minute and realize that everybody has different approaches to things. As far as pryo stuff, I actually have a very great knowledge of the field. So, if I ever have the need to learn how to detonate something, and i don't know how to, I will consult you. Thanks, rsbhunter
I I don't know you. What the circuit does needs detailing and also others will read this. The detail of what the circuit does may be relevant to a person who doesn't understand that the simplistic representation of a circuit can hide a lot of detail. And current limiting for both the test and fire are important details.

Well I did some testing with new batteries in my Estes Electron Beam launcher after 2 min. with continuity check on a motor igniter it did not fire it. I then pushed the launch button and the igniter smoked for about 5 sec. or so and then the pyrogen ignited. With an e-match it ignited the instant I checked for continuity (inserted the pin). So Estes igniters are more sensitive than MPR/ HPR motor igniters. Makes sense seeing 12v systems are used by most of us. My post on the simple circuit was just to show how simple a launch controller can be. Bottom line do not use a stand alone light bulb for continuity check, especially if using e-matches for igniting motors, (CTI).
I wanted a simple launch controller also like rsbhunter and 20+ years ago when I made mine did not want a bunch of bells and whistles that needed diodes here and resisters there. I just wanted one that checked for continuity and launched the rocket.
What I did was used the same circuitry as an Aerotech Interlock Controller. I have an arm switch and fire switch. The arm switch runs thru a piezo buzzer to check for continuity, To launch, both the arm switch and the fire switch have to be pushed. Pushing one or the other will not launch the rocket. So using a piezo buzzer rather than a light bulb for continuity check is safe and don't need a resistor here or one there. Plain and simple.

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This circuit is a BAD example of a launch controller.

It is a representation of the ESTES electron beam controller. The circuit TEST current limited by the SPECIFIC bulb supplied with the ESTES controller and is suitable ONLY for estes MODEL ROCKET IGNITERS. The reason for this is that the ESTES igniters are very INSENSITIVE and you can put a lot of current through them without them firing. You cannot do that with other igniters or e-matches.
The circuit presented does not show the functionality of the SAFETY SWITCH operation activated by the conductive steel pin supplied by ESTES with the controller.
Additionally, the really thin wire that ESTES supplies as part of the controller to connect from it to the rocket motor with the igniter fitted act as a resistor and current limit the draw from the AA battery cells.
The circuit looks simple when drawn out simplisticly here, but is not.
Goodness!

FYI, Estes has been using LEDs for continuity indication in their controllers for at least a decade resulting in continuity check currents of <25mA (measured). This is ~1/6th what the continuity check current was when they used incandescent lamps.

Goodness!

FYI, Estes has been using LEDs for continuity indication in their controllers for at least a decade resulting in continuity check currents of <25mA (measured). This is ~1/6th what the continuity check current was when they used incandescent lamps.
I did not know that!! The 2 I have, have been sitting in a box for over a decade. Both have the good old incandescent bulbs. Like I posted above set off an e-match instantly when I inserted the pin.

I did not know that!! The 2 I have, have been sitting in a box for over a decade. Both have the good old incandescent bulbs. Like I posted above set off an e-match instantly when I inserted the pin.
With an incandescent lamp, I'm not surprised. The same was true of the late lamented Quest Q2G2 igniters.

Our club's old 10-pad panel has incandescent continuity indication, and we have learned that ematches and Q2G2s have to be expected to go as soon as the pad is selected. It does not lend itself to an LED retrofit like you can easily do in an older Estes controller (all the way back to the Electro-Launch by simply replacing the lamp with one of these: https://www.pinballlife.com/ablaze-...d-4447-bayonet-base-lamp-with-clear-dome.html I use the warm white color as it simulates the old incandescent look reasonably well. I have done this with a bunch of vintage launch controllers from Estes and Centuri and MPC.

Goodness!

FYI, Estes has been using LEDs for continuity indication in their controllers for at least a decade resulting in continuity check currents of <25mA (measured). This is ~1/6th what the continuity check current was when they used incandescent lamps.
Yes...... But that wasn't the circuit presented and the link was to an OLD electron beam controller.

Electrically, save for the type of continuity indication lamp (incandescent or LED) and the introduction about 15 years ago of the "spring loaded" continuity key (with that little bit of rubber tubing) these controllers have been electrically identical all the way back to the Solar Launch Controller of 1973, and really even the Electro-Launch and Launch Control Systems of the mid to late 1960s.

That rubber bit makes the key not want to stay in, which becomes the spring loaded momentary switch in the schematic. A schematic of current Estes controllers would look exactly the same. The "light bulb" is now LED-based. That's the only difference. (The recent Aerotech Phaser 9V launch controller has a real spring pushing back on the key to achieve the same result. It, too, has an LED for continuity indication.)

As noted above, putting an LED lamp in place of the incandescent renders even the earliest of these controllers safe for low-current igniters unless you've got something that fires on 25 mA.

Perhaps all this obsession with currents will better answer the OPs question, though, since that's really the important parameter, as has been noted in this thread.

I feel like I'm back in my early '80 Navy Basic Electricity and Electronics course.

A LED takes 2.0 volts and .020Amps to light up. Plug those values into Ohms law and determine what resistance you need with the voltage you are providing.

If you have 12 volts, you need to drop 2 volts across the LED and 10 volts across a resistor. R=E/I where I is .020 A and E = 10V so R = 500. Use a 480 ohm (standard and common value and cheap resistor) in series with the LED. Put 12V at one end and ground/return at the other and the LED will light without burning out (check polarity) because the current will be limited to about 20mA (.020Amps). BTW, Wattage = E*I so 12V x .020Amps is 0.24 so a 1/4 watt resister will work just fine. Most resistors are ±10% do don't overthink it. Close is OK.

To fire an igniter, you want the full 12V to be applied to the igniter with no resistance in the circuit. To test continuity, you want the resister and LED in series in the circuit so the current is limited to the 20mA. If the LED lights, it's because the igniter completes the circuit. If it doesn't light, you have a bad/open igniter. Pretty simple.

If you are using a tool battery that's at 18 - 20 volts, you will need a 900 ohm resister with the LED, so a 1K Ohm standard and cheap 1/4 watt resistor will work just fine.

This is basic electricity and electronics, NOT rocket science. If you don't understand, the sparkfun learning website will teach you.

Have fun and learn lots and launch lots of rockets!

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Well I did some testing with new batteries in my Estes Electron Beam launcher after 2 min. with continuity check on a motor igniter it did not fire it. I then pushed the launch button and the igniter smoked for about 5 sec. or so and then the pyrogen ignited. With an e-match it ignited the instant I checked for continuity (inserted the pin). So Estes igniters are more sensitive than MPR/ HPR motor igniters. Makes sense seeing 12v systems are used by most of us. My post on the simple circuit was just to show how simple a launch controller can be. Bottom line do not use a stand alone light bulb for continuity check, especially if using e-matches for igniting motors, (CTI).
I wanted a simple launch controller also like rsbhunter and 20+ years ago when I made mine did not want a bunch of bells and whistles that needed diodes here and resisters there. I just wanted one that checked for continuity and launched the rocket.
What I did was used the same circuitry as an Aerotech Interlock Controller. I have an arm switch and fire switch. The arm switch runs thru a piezo buzzer to check for continuity, To launch, both the arm switch and the fire switch have to be pushed. Pushing one or the other will not launch the rocket. So using a piezo buzzer rather than a light bulb for continuity check is safe and don't need a resistor here or one there. Plain and simple.

View attachment 642385
Ditto...to a point, the KISS method has its merits. I do plan to have a led to show that the 12v in is good...rsbhunter

Ditto...to a point, the KISS method has its merits. I do plan to have a led to show that the 12v in is good...rsbhunter
Use an Ultrabright Red 5mm LED with a 680 Ohm resistor. This is a standard value available from any electronics supplier. This will keep the test current under 20mA and will be bright enough in all conditions.

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