Eggfinder Auto start

For those of you that have been using the egg finder, Chris has come up with an auto start fix.
I modified a unit that was already assembled. Pretty easy to do if you are careful. Note, (the sides of my board are shaved down to fit a 24mm nosecone)
You can use the following:



Steve:

Hey, Eggtimer Rocketry is a real job (too...)

OK, here's what you need to do. I'm assuming that you have NOT assembled it yet...

o Assemble per the instructions, but leave off the following parts:

o ATTINY85 processor
o .1 uF cap above ATTINY85
o Push button switch
o The GREEN LED
o The 2.2K resistor next to the GREEN LED

If you HAVE assembled it, carefully remove the ATTINY85 processor (be careful not to lift any of the pads!), the GREEN LED, and the 2.2K resistor next to the GREEN LED. The other parts can stay, they're just not doing anything anymore.

Now, with a piece of very fine wire (I recommend wire-wrap wire, 30 ga) jumper the LOWER-RIGHT pad of where the ATTINY85 processor would have been to the UPPER pad of the 2.2K resistor that's next to the (removed) GREEN LED.

That's it. Assuming all of your solder joints are good, as soon as you connect power the RF module should start blinking, approximately once per second.

Cris

Interesting. What is the advantage of this?

blackbrandt said:

Interesting. What is the advantage of this?

Click to expand...

It allows you to turn it on at the pad with an external switch.

So the ATTiny basically only functions as a power switch? Interesting.

timbucktoo said:

It allows you to turn it on at the pad with an external switch.

Click to expand...

Yeah,

The other deal is if you dork or break the Maestro Sirf4 GPS receiver, one can use an outboard GPS that can handle 3.3V and put the signal in wire at the lower left corner pad of where the Maestro is mounted in the above
photo. You can pull the 3.3V off the accessory terminals on the tail end of the board.

I was able to salvage a broke board in this fashion with a Ublox chipset. Kurt

HHaase said:

So the ATTiny basically only functions as a power switch? Interesting.

Click to expand...

Well, yes and no. It puts out timed pulses that tell the GPS module to start up or go into "sleep" mode. The advantage of doing it that way vs. auto-start is that you can power it on and wait for the fix, then put it to sleep until right before you get to the pad. In sleep mode, the satellite positions in memory are retained but the serial output data isn't sent; when you turn it back on, it doesn't have to go looking for the satellites so it starts up quickly. That can save significant power, if you actually use it that way. If you simply turn it on and leave it on, it's the same as the auto-start, it comes on and just streams out whatever data it has available. I think most people just press the button once, so auto-start may be and advantage for most users.

The TRS uses auto-start; there's enough complex stuff going on that I really didn't want to complicate it by trying to do the GPS sleep mode.

On my 24mm F Class rocket set up is a little complicated since everything is in the nose. The battery is shared between the Eggfinder and the Easymini altimeter. In the past I would start the GPS and finish installing the nosecone. I could start the Easymini with a screw switch on the pad but the GPS is already running and using power. At a busy field this can cause problems due to wait times. If I power up the GPS on the bench it locks in on the local signal. Normally if I re-power within an hour the GPS locks in a minute or so. Auto start allows me to prep everything on the bench and then power everything down. I then power everthing on the pad right before flight. Alll I have to do is wait for the receiver to start tracking and I am ready to go.



Thanks again Cris for your help on this.
I will be trying for 6000ft in a few weeks.