[ttshaw1]

I don't like the notion of doing speed control by putting a digipot in series with a motor. It worked because the fan happened to be low enough power but it doesn't seem like the author gave thought to the power handling capability of the digipot. If the fan happened to be beefier he's letting the smoke out with this design.

Plus, this is more complicated than just doing PWM.

[_ihaque]

Based on the description of the wiring to the motor (24V, GND, POT1, POT2, NC), it doesn't sound like the original setup would have been drawing much power through the pot either -- there's probably something else on the other end of that wire that is doing modulation based on the sense resistance, and the motor is itself drawing power from the 24V line. So while it's true that there should be a check for the allowable limits on the digipot, I don't think it's actually being used to sink much power.

[announcer4614]

Hey, author here. That's correct. The potentiometer has 5V going through it, with a current range of 30-164μA, which fell within limits of the digipot. I opted to use the digipot instead of my own PWM because something else must be doing PWM closer to the motor, where I didn't want to go modifying.

[ttshaw1]

You're right, I didn't read thoroughly enough.

>Everything joined up via a 2-pin and 5-pin connector on the PCB. From there, it was a straightforward matter of measuring voltages and continuity to work out what connected to what: the 2-pin connector was offering 24V DC. The 5-pin connector was what went off to the motor itself. Two of its pins were passing through the 24V DC and ground directly. Two more pins were connected to the potentiometer. The fifth pin was not connected.

[05]

> there's probably something else on the other end of that wire that is doing modulation based on the sense resistance

And it would have been great if that arbitrary assumption had been tested by the OP and the results were documented in the article so that they wouldn't come off as somewhat clueless as to the limitations of their design.. oh well.

[anamexis]

From the HN guidelines:

> Be kind. Don't be snarky. Converse curiously; don't cross-examine. Edit out swipes.

> Don't be curmudgeonly. Thoughtful criticism is fine, but please don't be rigidly or generically negative.

[TylerE]

These passive aggressive posts are a far worse violation of the HN Guidelines than what they're in reply to almost all of the time - and this is no exception.

[knappe]

No, no they're not. I would much rather people are warned about the guidelines and adhere to them going forward than the opposite and we then just let violations run rampant.

[TylerE]

They're not "warnings". They're passive aggressive internet dick waving virtue signalling. The flag button exists.

[bsder]

There are a lot of people who read or watch stuff from the Internet and then play with mains voltages without giving a though to how dangerous that is.

See: any craze which uses the high voltage transformers from microwaves