DC voltage regulator has serial interface and charging LEDs - Page 1
Forum section: electronics / beginners

author: Lycaon
author_rank: Contributor
timestamp: December 21, 2015, 04:03:16 pm
content: Well, a lot of the info is in the title, but I picked up one of the following regulators to stand in as a poor man's bench supply:http://pages.ebay.com/link/?nav=item.view&id=400544557141&alt=webIf you check out the details page, it shows a charging and a charged indicator LED one one side. Question here is, why would a voltage regulator need these?Second oddity. There is a three pin plug for what is apparently a serial interface. Again, why would a regulator need that? I assume there is a microcontroller hidden on the underside which is managing the LCDs but not sure why you'd need a serial interface.Third, I'm curious about the "reserved" plug bear the output side as well...Does anyone have a data sheet on this thing, or any insight on it? It works great, I just wonder if there are cooler things I can do with it that I am not aware of.I might be willing to pop the two boards apart to get pics of the inside, but not willing to dismantle it all the way. If it weren't for the fact that Dave lets his mailbag stack up for months at a time, I'd buy another to send in for a teardown.Edit: I'll definitely see what chips I can read and post them here when I get home in a few hours.Thanks in advance.

author: mariush
author_rank: Super Contributor
timestamp: December 21, 2015, 07:06:54 pm
content: They probably reuse the base board as a lithium-ion battery charger, with the potentiometers configuring the maximum voltage and maximum current allowed.They probably buy the microcontroller with a pre-programmed bootloader with serial interface exposed to upload firmware through it. Or, again, maybe they just recycled the top board from another project which used to expose a serial interface.

author: Rick Law
author_rank: Super Contributor
timestamp: December 22, 2015, 05:10:13 am
content: Quote from: Lycaon on December 21, 2015, 04:03:16 pmI am no expert but I have used similar boards "PSU". I have used half dozen of them. They are similar but not exactly like the one you are showing. But I think it would operate the same way.Thechargingindicator is lid whenever the current is below thecurrent limityou set. As the "battery gets full", current drops. Once it drops to what you set for "saturation"/"charged", it turns thechargedled on. Depending on design, saturation-current may be set as a percentage of current limit.Typically, current-limit is selected by shorting the output and then turn the screws on the trimpot to lower the current. With current limit set, you can proceed to set the "saturation percentage" or "saturation current". Now you lower the current to what you want as saturation-current, and turn that trimpot to make the LED just barely lid.This one obviously is different than mine. So it may work somewhat different.These things may be of interest:1. The current limit is likely going to bevery roughin the +-20% range and probably will not work below 50mA. Limitation caused by the offset voltage of the opamp and the current-sense "resister" which could be just a wiggle zig-zag trace on the PCB as one of mine was for a mere 0.02 ohms. So, it takes quite a bit of current to reach the Vos of the OpAmp. (Measuring with my DMM directly would not be very accurate for ohms that low. So I measured the mV-drop for 1 to 2 Amp current to evaluation the resistance.)2. Any change in voltage may have a significant impact on your current limit setting.3. If you do end up using one, make sure you supply it with a good power brick. Initially, I had some unexplained failures. In my case, as it turned out, a sudden and significant current increase cause the op-amp to fall below operational voltage. So, the output regulator goes full throttle, which continued to pull the voltage low enough for the op-amp to locked into a too-low-to-work voltage. Once I changed the power-brick, I had no such problem anymore.Other than the above, and noise, using those boards as "PSU" worked rather well for me. It was an adequate choice when I initially (re)started playing around with electronics and didn't want to spend a lot. I have since upgrade to an all-digital solution. The $16 MingHe B3603.Hope this info is helpful to youRick

author: Lycaon
author_rank: Contributor
timestamp: December 22, 2015, 03:46:01 pm
content: |ORhanks for the replies, guys.