R/C Backup

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I am building an R/C backup system for my Sandhawk.

I already have a model aircraft radio system so all I need is a switch that plugs into the receiver.

I plan to use a PIC to accomplish this. It will read 3 channels of the receiver, one for arming and one each for apogee/main deployment.

This is the schematic.

Here is the PIC program written in part C and part assembler.

I created a trace pattern for this circuit. Here is a PDF. Just print it on transparency using a laser jet printer. Then iron it on the pc board. Details here .

You will notice there are fields that need to be filled in using an etching pen. I have found using the toner transfer technique that small traces transfer well but large areas dont transfer well. Thats why I try to use only small traces then just fill in the large areas. Also I have found that you should mask off any large unused fields of copper. I usually just connect them to ground and make a 'ground plain'. If you have large areas of copper that you are trying to etch off it will cause the other areas of the board to etch unevenly and even etch under the mask. I have actually had thin lines get etched away because of this. Now I just try and cover any extra area and only etch away what I need to.

This is a picture of what it should look like. Here is the component layout.

Function:

The unit will read 3 channels from an R/C receiver.

At power on a continuity check is done. You will receive 1 beep for continuity on channel one and two beeps for continuity on channel two. In all you should receive 3 beeps if using both channels.

Then it goes into a loop checking the 3 channels for a pulse width of 1.7mS or longer.

Whenever the arming channel is active the buzzer will sound to indicate this.

At this point you can activate either the drogue or main to fire that channel.

RC nosecone

I installed the RC circuit and receiver into a nosecone. I figured this way I could easily mount it to any rocket for backup of the main deployment.
It also adds nose weight if needed. It only implements one of the pyro channels.

Here are a couple of pictures of the setup. PIC, PIC

Mail to Robert DeHate

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