I really like Marty’s ideas of making double sided boards and the auto shutoff feature when a certain conductivity is reached. A digital readout would just be amazing.

As others have requested, I too would really like to be able to buy a kit. But if that isn’t possible, pre-made boards and pre-programmed chips would be a HUGE help.

I’m like several others here can put things together well but am lacking in the programming, board making department, but that isn’t to say I won’t jump in and try it.

I am at a point where I really want to get this done. I would really like to incorporate Marty’s improvements if possible.

Marty, if you’re reading this, what is the status of your project? Can you give us an update?

Thanks again!

When you adjust R13, it goes from 0V to 3.2V, or does it just stay at 3.2V the whole time? Did you check the voltage at pin 5 when adjusting R13, does it go from 0V to 5.45V as you adjust R13 from one extreme to the other?

Are you getting 12V, or above, out of your wall wart / power source ( is that the voltage at the collector pin of Q2 – stirrer_output_hi on the schematic )?

At any rate, I’ll email you an updated hex file with the /2 removed, and we can see if that will help. You should notice the average voltage at the fan leads double just by doing that.

Cheers,
Morgan

OK…. the pwm scheme is what I was thinking was going on.

After further testing, I get an avg 3.2 V with R13 all the up. Freq is about 112 hz.

Still not enough to run the stir motor (fan), it will hum, but no spin. Maybe I will need the alternate hex file for the pic? It may have something to do with tolerance specs adding up in components the wrong way.

Thanks for your help, it has been a fun project!

Dave

Glad it is working for the most. For the fan, have you tried adjusting R13, the 10k potentiometer that is used to adjust the fan speed?

The fan drive is software pwm, so you will not see 12v at the fan leads unless R13 is cranked all the way up. Even then, due to R14 you will only get 4.54v max on pin 5, and in software I divide the adres value by 2, as I found in my setup the pc fan spun way two fast. That being said the fan should see no more than 4.54v average ( as it is pulsing 12v ) on your meter when R13 is cranked all the way up. Also make sure stirrer_out_hi is 12v with reference to ground.

To test further check the voltage on pin 5 of the pic12 micro. You should see that swing from 4.5v to 0v as you adjust R13.

Then if that looks good, check the voltage at the base of Q2, or pin 6, of the micro. You should notice that swinging to different voltages as you adjust R13, though it will be a bit different than pin 5 as this is the drive pwm output for Q2. Also, if your meter can do it, check the frequency on pin 6 when it is running, and make sure the stirrer enable switch is on.

One other thing, make sure the pickit is disconnected prior to running the tests, as it could be interfering with some of the i/o pins if it is still connected.

I hope this helps you get started to narrowing down the issue. Also check the traces on the PCB and make sure the aren’t any shorts, or pieces of snipped wire floating around on the board.

If everything checks out, I can get you an updated hex file with the /2 ( 50% duty cycle ) limiter removed.

Morgan

Happy New Year!

I have finished this project and all is working EXCEPT… I can only get 3v max to the fan out lines. (Fan hums, but not enough V to spin)

Any thoughts on what to look for? Best as I can tell, all the compnents in that part of the circuit measure properly.

Any suggestions would be appreciated:)

Thanks,
Dave

I am interested in contacting you about your design and making it
better with a selectable ppm output with an auto shutoff feature that it seems is being discussed.
I am interested in covering the cost for the production of this new design and possibly make them available at a cost that would cover production.

Chris

Thanks so much for the quick reply!

Your spreadsheet with part numbers and descriptions are second to none and it has been a bit of a treasure hunt this morning as I source the parts. I’m happy to say I have sourced all the parts with the exception of the PICKIT3 controller which I believe I have located at a good price.

This should be a fun project! I don’t have a lathe to create the laser enclosure, but I do have a Printrbot 3D printer! I’m sure I can whip something up in SketchUp and print a reasonable facsimile.

Regards,
Garret

Any .1uF cap will work fine as a replacement. I used mouser as a way to provide a reference to the part, and hopefully for it to be purchased, but their inventory is always changing unfortunately. If you find any other part having less availability, searching on there for a similar part should yield an appropriate alternative – of course don’t hesitate to ask if it is something more specific like the micro controller, etc…

Cheers,
Morgan

I was going through ordering the parts on Mouser when I came across the Ceramic Disc Capacitors 50V .1uF Y5U 20% Tol.

Mouser’s minimum quantity on this part is 200 pieces!!
Mouser does have this Ceramic Disc Capacitors 50V .1uF Y5U +80%/-20% Tol that can be bought in singles.

Is the tolerance going to be a big deal on this cap?

Thanks much!

Garret

No prob on the quick reply. Sorry on the board layout – for some reason the cap on the board layout doesn’t show the polarity, if you look at the schematic you will see the proper polarity on the electrolytics, but they should all connect to ground which would be where the negative leg goes.

Let me know if anything else comes up,
Cheers,
Morgan