need help

BebopALot

Hi folks,

I want to slim the size of my prototype down a lot and need to custom make my own protoboard version of the SX-48. Does parallax offer a kit of the supplies (e.g. socket, Sx key connector, header, etc)? Also is there any documentation from anyone who has been there done that so I can avoid mistakes and pitfalls?

LoopyByteloose

The Sx-48 protoboard comes without headers attached [noparse][[/noparse]excepting the SX-Key plugin]

I suppose you ask Ken to provide one from a 'mid-production' run. It would have the ICs in place, but you would have to solder the rest of the components as you see fit.

The real problem here is to determine what 'mid-production' is and how to pull just one out of process taking place in Asia for a customer in the US or elsewhere.

Seems like desoldering is the most realistic alternative. You could see about a SX-Chili on E-Bay for a smaller footprint.

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"When all think alike, no one is thinking very much.' - Walter Lippmann (1889-1974)

······································································ Warm regards,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

Paul Baker

BebopAlot, Ive got good news and bad news for you. The good news is that Parallax used to have a reduced size prototype board for a larger SX chip,·it was discontinued about a year ago, and upon my request they released the Gerber files for the product. The bad news is it was for the SX52, which is now also discontinued and there is no stocks of the chip left (I have 2 of them but wouldn't be willing to part with them).

Here is the link to the thread where the gerbers were posted: http://forums.parallax.com/showthread.php?p=539600

You are not the only one to express interest in a reduced size protoboard for the SX48, the layout for the SX52 con carne should be fairly easily adapted for the SX48, I unfortunately dont have the time to spare on such a venture at this point.

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·1+1=10

Post Edited (Paul Baker) : 1/19/2006 4:12:47 PM GMT

Tbag

I talked with tech support today. They referenced the schematic for the protoboard: http://www.parallax.com/dl/docs/prod/boards/SX48-52ProtoBoardDoc.pdf
Basically collect the parts, build it yourself, which I am fine with. I could use some help sorting through the parts though. If I know I am going to use a 75MHz resonator, I won't need the X1 or X2 socket or Cx sockets. If I put this on a PCB I can just solder the resonator in with the appropriate spacing without a socket. I only need a two state switch to go to digital logic. I'm not using servos. I'LL DEFINITELY NEED A RESET SWITCH ... HA HA HA.

(2) Questions to Paul, Kramer,or anyone else

1. How the heck do I solder the SX48BD assuming I have a PCB made. Tech support said he has done it plenty. Can anyone help me with this?

2. I don't understand why there is an LM2940 on the board if the there is already a regulated PS from the wall. And if I use a higher input voltage (my current setup uses 40V) do I need to change out the 2940?

Much appreciate anyone who could give me a clue on these two questions.

Paul Baker

Rather than reiterate the various techniques people use, here is the most recent thread on the topic: http://forums.parallax.com/showthread.php?p=565477

You'll have to consult the tech docs for the regulator to see if it is compatible with the higher voltage. With such a large difference between the supplied voltage and the final regulated voltage you should look into a DC/DC step down voltage regulator. The old type of regulators dump the excess voltage as heat, the more difference in the two the more heat produced. The switching type of regulators do a much more efficient job at converting the voltage with much less generated heat.

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·1+1=10

Post Edited (Paul Baker) : 1/19/2006 6:50:06 PM GMT

Tbag

Thanks for the patient responses Paul. I have to say the suggestions look, well, daunting to someone who solders basic components infrequently. Fortunately the chips are not that expensive if you flub it. I can do the same job to meet my needs with 2 binary counters, two Johnson counters and a few gates. It will take up much more room though, but my confidence is a little better with these. I have to say that I tested the stability of the SX making 40KHz driving waves and seemed just about as stable on my o-scope as a pure crystal+inverter oscillator...oh wait, the SX has crystals, inverters and oscillatates!

My main issue is soldering. If I can over come that, no prob.

Paul Baker

I just recieved a Ramsey Electronics catalog and they have a SMT soldering course for $21, the link to it is http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=SM200K

I can't tell what thier smallest pitch part is, but it should be a good way to practice your technique before trying something more important.

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Guenther Daubach

BebopAlot,

concerning the voltage regulator, please Google for the LM2574 switching drop-down voltage regulator from National Semiconductor. Since a while, I'm using it in many applications without any problems. Just two caps, one inductor, and a Shottky diode plus the LM2574 make up a fine regulator with good efficiency, a wide input range (up to 40V, or 60V with the HV device types), short circuit and thermal shutdown protection. There are available for 3.3, 5, 12, 15, or adjustable output voltages, 500 mA curent max. Similar types are also available for higher output currents.

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Greetings from Germany,

G

BebopALot

Thanks for your help everyone. Here is an update for those interested in seeing what happened:



http://forums.parallax.com/showthread.php?p=568099