Interesting power supply
I got one of these off Amazon: https://www.amazon.com/dp/B0C9MYFMHH?ref=ppx_yo2ov_dt_b_fed_asin_title
It seems to be a cheap ($15) linear adjustable-voltage adjustable-current power supply. It's a kit, and it's not easy to build as there are no instructions and some spare parts provided. The build is entirely using the board markings. I've just started playing with it, but on the o-scope it looks completely flat, no noise at all. I've yet to test it on the KiwiSDR and an AM hobby transmitter.
The silicon parts are three op-amps and five transistors.
It needs AC power to run. The page says DC but it's wrong; the circuit starts with a full-wave bridge and big capacitor. To get the rated 30vDC out you must provide a 24VAC input, but I can get up to 15.5vDC out using a 12vAC input with no load. It'll be less when I load it up, I suspect. I think the LED illuminates when the output is current-limited.
Once I get testing it with 24VAC input (coming on Tuesday) I'll post again how it performs on the KiwiSDR and on the AM transmitter.
Comments
You will definitely need to put that regulator on a decent heat sink running the kiwi 24/7.
I just bought one of these:
Most excellent for the price. Very clean. Runs cool.
With any adjustable power supply, once you have determined the correct settings for your application, I'd suggest replacing the variable resistors with fixed values.
It's so easy to accidentally knock the controls and fry any kit that is connected downstream, that I think it's a sensible precaution.
With any linear power supply, I'd also add a simple overvoltage crowbar circuit, consisting of a SCR, Zener diode, two resistors and a capacitor.
In order to reduce the amount of heat generated by the linear regulator, you only need the smoothed DC to be a few volts above the regulated DC output, and using a larger than recommended heatsink, will also improve the long term reliability.
Regards,
Martin