Payalneg

yes, it is

Dentdog

Does anyone have the parts list to make the transponder? I emailed Howard but never got reply.

howardcano

iTrader: (37)

Lost in the bit bucket. PM sent.

30Tooth

iTrader: (1)

Great news and good job!

Acadi3n

We started assembling one of your transponder Howard, and we are looking where to put D1.

If I understood correctly, D1 is used to regulate the power to 5V in case more power would be sent from the receiver. So technically, if the electronic speed control on the RC has a limited 5v output for the receiver, D1 would not really be required, but if someone have a ESC that can be programmed to output more voltage to control "hi-voltage" servos, ther, D1 is required.

Looking at the schematic, I see where it should go, but I'm trying to figure out where to install it on the PC Board. Would you have a picture of one installed?

howardcano

iTrader: (37)

Your analysis is correct.

D1 is missing on the PC board. My apologies for not creating an errata post stating this.

On the rev 2 boards I soldered a through-hole Zener to the back of the board. There are several possible locations where this could be done; an example is cathode to square pad on C1 or U1, anode to round pad on J2. (J2 can be omitted, since it currently serves no function.)

I had purchased a few surface mount Zeners to use on the rev 3 circuit board, but never got around to making the board. I had intended to put it in place of C5, figuring that C1 alone was sufficient bypassing.

Acadi3n

We are using your Rev3 of the board (PT_R3 6_11_13). where would be the ideal place to put D1 ? C1 to J2 seems far

howardcano

iTrader: (37)

If you are using a through-hole Zener, then any convenient pads of the correct nets will do. Cathode goes to +5V, anode to ground.

If you have an appropriate surface-mount Zener, then put it in place of C5.

funked1

iTrader: (10)

This is awesome, keep going guys!

mv4wd

I've been able to follow your ideas and make my transponder. The schematic is slightly different from Howard's one, I'll try to post it in the next days. One thing I don't understand is if someone has been able to encode his 'favourite' number. I understand that's possible to decode the bitstream and get the transponder number, but, beside a CRC number, each digit 0 or 1 number can be encoded as '00'-'11' or '01'-'10'. Payalneg hase done some brute force encoding for the CRC? I suppose some sort of code correction coding is used and a bad encoding might lead to false reading or low S/N ratio.

howardcano

iTrader: (37)

That's great! I'm looking forward to seeing your design.

Acadi3n

We have build our first transponder yesterday. We made Howard version, based on specs received, parts BOM and PCB layout. We used rev3.

However, it doesnt seem to send a strong signal, almost as if the antenna would not be connected. As I further looked at the schematic and the pcb design, I think I have found a little thing.

We were told that CT1 and CT2 were not used, but if you look closely on the PCB layout, it creates an open loop at the antena (if I see it right). Would it be safe to install a jumper at CT1 and CT2 ?

mv4wd

Here it is. I'm using a PIC 12F1840 that contains a modulator. The carrier is taken from the system clock, the internal PLL x4 multiplier allows to have four instructions for each bit sent (20MHz clock). This means you have to bit bang the modulation bit every fourth instruction. The two drivers are two not gate paralled, a not port is used to get the out of phase modulator output. I've tried using the internal pic comparator to get the out of phase signal, but it's too slow . Since max rated output is 25 mA, I wonder if only the pic can be used (single ended driver). Unfortunatley my oscope is acting strange so my experimentation is in standby. This was a very interesting project. Lessons learned: more PIC programming , the Microchip emulator does not emulate the modulator , the 12F1840 needs a low voltage programmer , tried to modify the JDM but didn't work ... made a new programmer , channel coding
Thank you all for the input... still wonder if I can program my favourite number.

mv4wd

They MUST be used. They are the output antenna circuit... or am I missing something? (I didn't read all the thread)

Acadi3n

My mistake, apparently!
I checked my noted and the only reason they were not included, is because no information about them were in the part BOM we received.

Could anyone tell me what part I need to order from mouser?

Also, is it possible that a connection would be missing between R3 round pad and C4 square pad beside it?