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brinkmann27 (Electrical)
13 Feb 08 10:43
We make a small PCB which controls a pump. We have an alarm/shutdown circuit which is delayed by one minute during startup. In the past we have used a solid state timer off the board and wire back to it. The coil voltage is 24 VAC and we have a SPST contact on the timer.

Ideally we would like to find a small delay on timer which will mount directly on the PCB. All the units we have found are standard timers using a PCB mounting block. The cost and size of these units are not acceptacle.

If there is a small PCB timer out there we haven't found it. Anyone know where one is?

Thanks in advance.
MacGyverS2000 (Electrical)
13 Feb 08 10:56
Perfect app for a small PIC chip, or a 555 timer IC if you're not a programmer type.

Dan - Owner
http://www.Hi-TecDesigns.com

itsmoked (Electrical)
13 Feb 08 14:56
Yes! If you're going to redo the board anyway, use a PIC.  Get someone to do it for you.  Won't take long and won't cost much. And you can have it work exactly like you want it too.

  With a wee bit of thought, you can probably add a useful feature or two also.  If you have adjustments on the present board to set the time, all that can go the way of the Dodo.

Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com

GonzaloEE (Electrical)
13 Feb 08 20:38
Agreed. An onboard PIC would cost less than a lot of hardware.  You could still put a 555 timer to one-shot mode or something, but...
The PIC12F629 costs less than $2, and the program should take < 2 hours of C code.
The C compiler is free:
www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en019469&part=SW007002
and there's a free (trial) C compiler:
microchip.htsoft.com/products/compilers/PICClite.php

There are dev. boards for less than $20, from 3rd-parties and 'officials'  
www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2122

There are also cost-effective alternatives from Atmel and Freescale Nitron family microcontrollers.  I don't know 'em well but it worth paying a visit to their sites.

Good luck with the board!
Gonzalo


richs (Computer)
15 Feb 08 13:31
Hiya-

Not to disagree with GonzaloEE. but the 12F629 might be overkill for the product.  It is a fine chip with lots of capabilities.  I have used the 12F675s a lot.  They are the same as the 12F629s with an a/d converter on it.

You might look at the 10F200 series of PICs.  These are even cheaper.  Don't have much memory nor ram, but they can do the job.  They are running about $0.60/chip quantity 100s from Mouser. The 10F220s which have a little more capability (like an A/D) run about the same price.

If you want to go to a micro, then there are all sorts of capabilities that open up to you.  A good consultant with a good statement of work might significantly reduce the parts count on the board.

Best of luck!

  Cheers,

    Rich S.

GonzaloEE (Electrical)
1 Mar 08 22:40
Thanks Richs. Each day there is a new micro with a little more stuff packed inside.
I'm also a happy PIC user for years (honestly, just avoiding a new learning curve and throwing away dev boards, hehe).  

Agreed an independent consultant could provide better guidance.  

Good luck with the BOM!

Gonzalo  
richs (Computer)
3 Mar 08 12:14
Hi GonzaloEE

I too agree on only learning what I need to do the job.  The intro to the 10F series was for a client.  I typically have about 4 of the PICs that I use off the shelf now.  The 10F parts (as mentioned earlier) the 12F675, 16F648 (now) and the 16F877 parts.  Will switch to the 16F88X parts in the near future.

Shoot, there is so much overlap on the PIC parts, half the battle is determining what sort of price/overkill you want to deal with!

Since the OP mentioned cost, I'm assuming that he is willing to swap the NRE (non recoverable engineering) costs vs. the number of PCBs he wants to produce over the lifetime of the board.  

For ease of use, the 12F629 *IS* easier to program/maintain/upgrade, etc. and is only a few pennies more per part.  Almost six of one and a half dozen of the other.

  Cheers,

   Rich S.
GonzaloEE (Electrical)
6 Mar 08 23:31
Hi Richs

Certainly, I guess each engineer has his/her own 'update rate' or balance between the time spent in learning new technologies, and the time spent gaining further experience with that (s)he already knows.

Also agreed that Microchip (like other vendors) always try to 'bulletproof' their products, so it's almost unavoidable to be paying for a chip with lot of features you will never use.  

Seems like 10F200 sounds good for this, as it only have the timer, a watchdog timer, and enough ROM for the needed application. Right to the point.

Regards,
GonzaloEE

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