PWM 16kHz Test - and more....

[soram]

OK I'm new to this forum but have done a little background!

I elected to build the RC1a version as a challenging / interesting project to get my hand back in....

I have sourced all the components and built both the alkaline and the LiIon battery boards. Both work fine. I've populated the power supplies and managed to program the ATMEGA to flash the LED. That was a bit of a pain as it took me 3 hours of messing trying to talk to the AVRISPMKII. Turned out to be a faulty USB cable supplied with the device......

Now, unfortunately, though I can program, C is not my strong point and the framework around the code is daunting for me.

I'm looking to do the PWM test for 16kHz but there is nothing obvious to comment back in the code. I tried test_DC() but it appears I get a pulse train with changing on/off ratios rather than a stable squarewave.

Anybody got any pointers here? Or should I just press on with the rest of the build?

Cheers

[soram]

OK it looks like I misunderstood.

The test-DC seems to be the correct one. At least when I do the next step I get the slow changing DC offset.

So all is good....except my 30 year old scope which just gave up its timebase.........

[TheFallen]

Unfortunately while the code works, and is in places elegant, on the whole its goddamn confusing, My best recommendation is to keep soldiering on.
Another option would be to write your own. I was thinking of Arduino-ising it, while would mean that you could upload new code Via the Arduino IDE.

[soram]

Thanks Fallen for the comment. I did indeed press on with the build and got pretty far after sourcing a new scope!

I got as far as soldering the PLL circuit but after I connected the power I got smoke out of IC1. I haven't had a lot of time since and not the heart really but now I want to finish it.......

So I've laid out my bench again and am looking to find the problem.

IC1 is not totally fried. It still delivers 3.3V and IC16 gives 2.5V from it for the PLL but after a second on the power it starts to smoke again. All the other rails are fine. Everything was good until I put in the PLL circuit but something is taking lots of power at 3V.

I have just noticed I didn't put any antennae on the VCOs as in the build procedure. Am I overloading it because of this? Might there be any other obvious place to look before unravelling the last build phase which would be painful as I can't see any obvious bridges.

Anybody any idea what length to make these wire antennae?

[soram]

Well I soldered in some 'antennae' but that made absolutely no difference!

I am powering up from 3 alkalines and the supply drops from 4.5 ish to less than 4V and the circuit takes about 700mA. I suspect it would take more if it could! I'd be afraid to put the Li pack on......

There is a faint audible whine on power up - I suspect between 5 and 10kHz.

Oh well - looks like I'll have to start unsoldering

[soram]

Just an update on the earlier problem and the project.

I unsoldered R29 as the supply to the PLL chip as a first start. The 3.3V rail settled down but I don't think that wsa the problem. In any case I just resoldered the resistor and replaced the 3.3V regulator and all was OK ! No idea why. Maybe there is a dry joint somewhere that I disturbed.....

So I then walked through all the testes again and finished the PLL stage. The got the PLL to switch for both VCOs for the two testes so I soldered in the gain stage and entered in the frequencies in the config.

All seemed OK. It says it tunes up. Anybody know if that means it really has?

All good except it is not doing the business! My phone is right next to it but still got full bars! I don't have anything fast enough to hand to check the actual output

Also, I get spurious programs. I might be lucky and get 1 but normally I get over 100 with arbitrary frequencies. This makes it a bit hard to know what program is running. Any ideas? When I cycle the power sometimes new programs show up full of rubbish. So that's not very useful. Anybody know what the problem might be here? Seems like the memory area used for the programs is volatile. Can I change that someway?

Cheers