I see 4 inductors if I zoom in on the board layout, L1-L4, one of them is pretty chunky.

Good eye. I see two, where are the others you see?

 

They are easier to find on this:

 

Hahaha. Apparently, they make their drawing available.

I would've thought the inductors were bigger.

 

Hahaha. Apparently, they make their drawing available.

I would've thought the inductors were bigger.

As a matter of fact, I don't think those inductors form the filter everyone thinks they do. There is no way you can drag 10 amps through those and not have them pop.

As far as the bigger L4, it is out of the way and connected to an LM2574 simple switcher regulator. Nothing to do with an LC filter for the peltiers.

This is a capacitor only board I believe.

 

As a matter of fact, I don't think those inductors form the filter everyone thinks they do. There is no way you can drag 10 amps through those and not have them pop.

As far as the bigger L4, it is out of the way and connected to an LM2574 simple switcher regulator. Nothing to do with an LC filter for the peltiers.

This is a capacitor only board I believe.

That was my thought too.
I wonder if that board can be programmed for Vmax limiting.

 

That was my thought too.
I wonder if that board can be programmed for Vmax limiting.

That is a very good question.

If my assumption is correct about what the capacitors are doing (smoothing out the PWM to a DC signal), perhaps it uses a standard voltage that is beneath most peltier modules and sources current accordingly. The controller has a 30 amp fuse on it; the specs say it can handle many watts of power control.

I do know that it comes with a serial port adaptor and a simple form application to tweak the PID loop coefficients, as well as a few other things; proportional band, etc. Maybe there is a control for this voltage.

I'm going to check tomorrow - now that you mention it.

 

They just use unfiltered PWM to the peltier device like most manufacturers, you only need filtered PWM if it is less than about 4kHz to reduce thermal cycling shock.

...
However, I also agree that it can be done with on/off control, but the equivalent switching frequency would end up being the same as my pulse-width modulation signal!
...

I wasn't talkng about on/off control but about high speed delta-sigma modulation.

Basically the same result as PWM (and similar high frequency output) but not limited to a low resolution, and the resolution is fully under your control, so if you need resolution of 1 million, or 10 million etc its up to you and just needs changing one constant in your code.

You can have a very high resolution power adjustment to the heater load (which makes the precision temperature PID so much easier).

 

They just use unfiltered PWM to the peltier device like most manufacturers, you only need filtered PWM if it is less than about 4kHz to reduce thermal cycling shock.



I wasn't talkng about on/off control but about high speed delta-sigma modulation.

Basically the same result as PWM (and similar high frequency output) but not limited to a low resolution, and the resolution is fully under your control, so if you need resolution of 1 million, or 10 million etc its up to you and just needs changing one constant in your code.

You can have a very high resolution power adjustment to the heater load (which makes the precision temperature PID so much easier).

I'll have to look into this. I did look at whether Vmax limiting was present on the controller...and it seems that it is up to the user to supply only the Vmax that is needed. I think Ron_H inquired about that a day or so ago.

 

I know this thread is quite old, but I searched the forums to figure out my handle (PaulEE) to become more active again. Merry Christmas and Happy New Year, +11 (nearly) years!

I am a lot smarter than I was when I posted this...I can only imagine how much smarter you all are! Cheers!

Paul
KI5VNH