Voltlog #155 – TL431 0-15V 0-5A Adjustable Power Supply Kit 3AG1 Xiaolin

A while ago I showed this power supply kit, which I ordered from ebay. It was being advertised as an LM317 0-15V 0-5A adjustable power supply kit and it looked promising. Upon receiving the kit and taking a closer look theres 2 thing to mention, one the power supply is not based on the LM317 but on the TL431, they used TL431s instead of op-amps in this power supply design and two there isn’t much documentation about this power supply.

The components used are low quality but that is to be expected from these cheap kits coming from china so no surprises there. If you would like to use some better quality parts I would suggest replacing the electrolytic’s and the TL431s with ones sourced from known sources. Also a nice upgrade would be to use some 10 turn pots instead of the supplied ones to get some finer adjustment. But I just used the originally supplied parts to see what kind of results we get with those.

Get the TL431 power supply from these links:

Here is a screenshot with the signal measured right on the bulk filtering capacitor (4700uF). Looks like this might be the cause of the 100Hz oscillation we we’re seeing on the output.

Here is a screenshot with the current overshoot. The power supply was set for CC 50mA and I suddenly shorted the output through a 1ohm resistor. The scope probe was placed across the resistor leads on the low side ( 1mV = 1mA ). As we can see we have a huge spike of current that could potentially fry an LED connected on this power supply. However the spike lasts less than 1mS which is good and I have observed similar behavior on my HP E3611A analog bench power supply.

Here is also a screenshot with the power supply regulating the current at 50mA in CC mode. This doesn’t look right at all.

Voltlog #71 – Electronic Touch Musical Keyboard Kit

A while ago I saw this touch musical keyboard kit on banggood and it seemed interesting enough to order one. It turns out the kit is using a single atmega8 to do all the touch sensing (8 ch) and play the tunes accordingly. Although not very useful for me it sure was fun to assemble and play with.

Voltlog #69 – LM317 Kit Assembly Fail

Sometimes, when I have some spare time I like assembling these cheap kits coming from China. Today I am assembling an LM317 adjustable power supply kit complete with voltmeter. Unfortunately they sent me a wrong resistor value so the kit didn’t work as expected but I was able to fix it in the end.

Voltlog #47 – ICL8038 Frequency Generator Kit Assembly

Today we’re going to be assembling this frequency generator kit based on the ICL8038 which I got in an earlier InTheMail episode. The ICL8038 waveform generator is a monolithic integrated circuit capable of producing high accuracy sine, square, triangular, sawtooth and pulse waveforms with a minimum of external components.

Voltlog #45 – Multiple Rail Power Supply Kit Assembly

In this video I am assembling a multiple fixed rail power supply kit. This power supply works with a 5-24V input either through a USB mini socket or a dc barrel jack (2.5mm center positive) and at the output you get +12V, -12V, +5V, -5V and +3.3V. My kit was missing 1 small heatsink and one of the electrolytics was a different value than specified on the PCB.

Voltlog #27 – Transistor Tester Short Functionality Review

In this episode I am testing the various menus on the Graphical LCD Transistor/Component Tester purchased from banggood. This gadget does more than just measure and identify components, it can also measure frequency, it has built-in frequency generator as well as a 10-bit pwm generator with adjustable duty cycle.

Links to the products shown in this video:


Voltlog #15 – Kit Assembly LED Rotating Persistence of Vision Kit

The assembly of this LED persistence of vision kit started well but it soon went bad because of poor design and lack of instructions. There is no documentation on how to assemble the mechanical parts so you have to figure that out yourself. There is no mention or pictures of how the LED’s should be soldered and to my surprise they need to be soldered on the edge of the PCB. There is no information on how to load the firmware or custom text patterns. After some research I did manage to find a chinese app which is supposed to work with this kit but I had no success in writing/uploading anything to the microcontroller.

I even spent an hour or so with google translate and, translated to english most of the buttons and messages in the app.

At this point I’m not sure if my problem is in the hardware(unlikely) or if I need to program the microcontroller, or if the microcontroller has some firmware and I just need to upload a custom display pattern using that chinese app.

Too much time & effort has been wasted so I’m not going to follow this anymore. My recommendation: don’t buy this kit unless you have too much free time and you enjoy solving complicated (chinese) problems.