Do you have a link for these linear power supplies, thank you.
Korad KA3305P "programmable DC Power Supply"
It's got USB and serial for PC connection, but mostly I just use the thing with the dials on the front.
There's nothing similar for the money. Siglent is similar quality but costs a bit more. Siglent are smaller and lighter (and likely costlier) because of their use of toroidal transformers. I have a couple of their 16V / 8A supplies with burnt output transistors (battery charge backwards oopsie lol)
You don't have to do this next part with the Korad- it's to fix its semi-loud disposition if you're so inclined. Most people might just put the thing in a closet or cabinet which will silence it well enough, you just have to remember that if the space is small and unvented, it will heat up eventually and you'll have to find how long it is before ambient temperature rises more than ~20-30C (running time limit)
Here goes for the Michael's Korad Kustomization and Konfig:
The fan in the Korad is one speed only, and for some strange reason, PWM is used.
Not traditional PWM though ("traditional" as in 12V is supplied to the fan along with a PWM signal on a third wire which is used to adjust speed).
It's PWM as in: "there are only two wires and the power
itself is pulsed..."
So, so weird, right?!!!
Extremely...!
And not weird like "only sometimes this configuration is seen". Weird like "this PWM isn't like anything else I've ever seen anywhere, in any device!!!"
The effect from
pulsing the power itself is unfortunate, too, probably especially so with the extremely low frequency that was chosen: ~150Hz
150Hz is a very low frequency for any pulsed signal
Anyway, what I did to remedy the situation is:
I put a 50-100 ohm resistor in line with the fan which serves two purposes. Since the top of the PWM pulses is too high to send to the fan 100% of the time, the resistor lowers that voltage to one that makes the fan spin at the right speed. It's second purpose is to limit the charge current to the capacitor I added which I'm about to tell you about now:
I added a 100-220uf capacitor to smooth the pulsed power being sent to the fan, into /more or less/ a stable voltage (it's pretty stable, the fan's speed doesn't flutter or wow).
Yes, I gave ranges. I'm sorry... The reasons are possible differences between components in different devices and possible differences of your preferences in fan speed control from mine (ie. how much heat you're willing to deal with - like an overclocker's CPU fan profile, for example). There's also the fact that I don't remember exactly which components I used, too. I do know they were in the range I provided, though. I'd take the cover off mine to look if it'd do any good, but it won't.... I heatshrinked around the parts to eliminate the possibility of shorts (I recommend you do the same unless you have other plans. In any case, make sure to make plans to minimize/eliminate the possibility of a short.
If you can't tell, tinkering with things is a hobby of mine, and to get this fan profile working the way I wanted, it took a combination of theorizing, strateging, and last but not least: trial and error. In the end, the above described description is the simplest and most reliable way to make the fan behave properly. As optimally as possible given its power source.
To Korad's credit, this is meant to go in a lab, and the sound level of most equipment in labs isn't really a consideration. The sound the thing makes while running is likely to only to be noticed by the operator in the lab using it because of the sound everything else is making.
What ends up happening when you incorporate the two parts properly?
0A-1A: The fan spins at about 400-500RPM and is nearly silent. The device stays cool, air exhausted from the rear maxes at around 35C
1A-2.5A: The fan increases in speed, from 500RPM at 1.0A, to 2300RPM at 2.5A. It's pretty linear (as in, at 1.75A, the fan speed it at about 1400RPM) and air exhausted remains around 35C. It's actually cooler at 2.5A than at 1.0A!
2.5A-10.2A: The fan spins at about 2300RPM and the air exhausted increases in temperature until it's about 55C at full power.
(When I say 10.2 A, there are two 5.1A channels. Whether you're using two channels at 0.5A each, or one channel at 1.0A, the fan speed will be pthe same.