No more switches

If you have seen my L3 build you will see that I have way too many switches on my AV bay. So I decided to build a circuit to make those go away. The RC folks have some solid state switches operated by a little button or two, but after watching a fellow rocketeer nearly loose a rocket due to one of these circuits I figured it best to start from scratch.

The current circuit design has two buttons and/or digital inputs to start and stop the solid state switch(es). It has two power inputs, one for an altimeter, one for pyro and the corresponding outputs. A push of the start button and everything comes to life. Press and hold the stop button and everything shuts down. Sounds fairly basic until you consider all the other crazy stuff that goes along with a rocket. If the incoming power circuit is noisy, maybe due to a bad weld joint in a 9V battery, etc. The circuit will remain in the on position and filter the power going to the altimeter so it doesn't reset in flight. Or say for instance a button starts shorting or triggering due to vibration, etc. The circuit assumes all inputs are startup commands unless the stop button is held in place for 10s while the start button is released. Maybe you have a low battery or some hogg of an igniter and when it fires it drops your voltage below the operating voltage of the altimeter. The circuit maintains filtered power to the altimeter while the pyro fires in addition it keeps the pyro and altimeter power circuits latched on.

Here is the first test of the power circuit with a TeleMega. Several boards will soon be released to beta testers. After testing I will make a production run and offer them for sale.





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Interesting idea. So this circuit basically acts as a debouncer for the (physical switch) button?

How many poles?

Very interesting. You have peaked my interest. If you need beta testers, I will volunteer and test it with other altimeters.

Funny you should bring this up... there may be some interesting things coming up soon. :wink:

I sent you a PM.... I volunteer to be a Beta Tester to test with RRC3, and RRC2+ altimeters.

If you still need testers I have a telemetrum,RRC2 and every egg timer product I could test them on.

I will help if you still need a beta tester.



TA

I actually like it when this happens - I feel like kind of an idiot.

I'm going to admit that I have no idea what you are doing here. I don't get it.
What exactly is this?
It SEEMS like you are eliminating switches with.........ummm.......a switch of some sort?

s6

stealth6 said:

I actually like it when this happens - I feel like kind of an idiot.

I'm going to admit that I have no idea what you are doing here. I don't get it.
What exactly is this?
It SEEMS like you are eliminating switches with.........ummm.......a switch of some sort?

s6

Click to expand...

The PCB regulates the voltage/current to many devices. That way instead of having 3 switches for 3 altimeters, there is one.

It sound like there are backup features. Just in case if the battery is not making a good connection for a little bit of time there are capacitors to keep the current to the electronics.

JohnCoker said:

Interesting idea. So this circuit basically acts as a debouncer for the (physical switch) button?

How many poles?

Click to expand...

Yes. It latches on upon press of a momentary start button and latches off upon holding the stop button for several seconds. Two poles(channels), one for the altimeter and another for a pyro battery.


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stealth6 said:

I actually like it when this happens - I feel like kind of an idiot.

I'm going to admit that I have no idea what you are doing here. I don't get it.
What exactly is this?
It SEEMS like you are eliminating switches with.........ummm.......a switch of some sort?

s6

Click to expand...

This post brought a smile to my face. Yep, you got it, eliminating a switch with two buttons, what the heck...

The circuit is meant to better guarantee power to your avionics. A single switch on a single battery has a few probable failure mechanisms we are all familiar with:

1. Intermittent internal connections within a battery pack, especially 9V batteries.
2. Loose wiring.
3. Bad switch.
4. Exceeding vibration or acceleration thresholds on a mechanical switch.
5. Excessive current draw.
6. Voltage drop out due to pyro ignition.
Etc.

The circuit reduces the above failures.

1. If the battery pack has a loose connection or momentarily looses contact during heavy acceleration the circuit will provide limited power to the altimeter to keep it running during the interuption.

2. If a wire is loose to the buttons or battery it will perform the same task as described above.

3&4. A physically latching switch is not required for the circuit(this is the dominate failure mechanism for mechanical switches being operated in high acceleration and/or vibrating conditions). A very small momentary push button is sufficient to energize the circuit. If the push button vibrates or shorts or whateve, the circuit doesn't care and just keeps the altimeter on. The only way to turn off the circuit is to push the stop button for several seconds with the start button released.

5&6. Excessive current draw on a single battery system can cause the supply voltage to drop below an altimeters operating threshold causing it to reset. This circuit can be used in a single battery configuration. The circuit will maintain power to the altimeter while the pyro fires. If your altimeter does not support a second power source for pyro's, no worries, my pyro SSR with continuity will be out soon.

I hope that answers a few questions.

NOTE: some beta testers have mentioned using a small push button mounted in side the AV bay and accessing it though a vent hole with a paper clip.



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BLKKROW said:

The PCB regulates the voltage/current to many devices. That way instead of having 3 switches for 3 altimeters, there is one.

It sound like there are backup features. Just in case if the battery is not making a good connection for a little bit of time there are capacitors to keep the current to the electronics.

Click to expand...

Yes, that is one way of using it. For redundancy I would recommend separate batteries, power circuits.

The altimeter output port has a small amount of backup power as well as the latching circuit.


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Thank you for all of the beta test offers, I will let you know if I have extra beta boards to test.


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