Optipower makes a great safety-product for us heliflyers, the Ultra Guard 430. The operation is very straight forward:
- Connected to receiver or gyro
- Senses when heli is powered up
- Starts to charge the 400mAh 2S LiPo
- Set’s output voltage 0,5V lower than input (from BEC or 2S LiPo, whatever You use)
Now, in case of BEC-, ESC-, or battery-failure where You would normally crash since there’s no power to RX and gyro the Ultra Guard gives power to RX, gyro and servos so You can (hopefully) do a controlled autorotation and save the heli.
After intentional disconnection of power You have to press the button on the Ultra Guard to shut it off. And this is boring. So we need to address that in the usual way, and that means Jeti-way.
Jeti is capable of sending a logic output of high / low on selected RX-output. Since the current available on that output is very low (rated to 1 mA according documentation of RX-firmware 3.22) we cannot for example drive a relay straight on that. So we need to do some thinking.
Solution is to make a logic-board and drive the on-off circuit to external equipment as a fet.
Since I know nothing about making anything I contacted a friend on IRC (as I have many times before) to discuss the subject. Our conversations are almost always the same:
- “Wouldn’t it be cool if…”
- “That’s actually easy”
- “What if we could also…”
- “How about if it could also…”
And after some weeks he has ready made PCB’s home and few days later I get letter with some parts to solder. I like the teamwork :)
Only difference this time was that it was SMD-components. Darn small… Surprisingly enough I got it together, tested and it works :)
Here’s the picture of complete setup, the new PCB is the smaller one. And it’s SMALL. Compare it to the normal-sized 2S LiPo balance connector on the left and You’ll get the idea.
Function is simple, when input (orange wire + brown ground wire) is high from the RX output (ie. when channel value is positive) the output pin’s are connected (Blue wires, connected parallel to Ultra Guard off-switch)
All I need to do is to do some Jeti-programming. I need to have some rules to make operation simple. Most simple step would be to use for example a rule “only allow when on hold-mode” or something.
Oh. You might wonder why? Laziness is mother of all good inventions. And to use a switch on heli is so 80’s :)