I spent 42+ years in aerospace with a company down the street from you but I always did the mechanical side. Now retired I am learning the electronic side of things and your videos are great learning tools. Keep them coming. Oh, I blamed all the new tools and supplies on you. :)
Zener diodes are devices with a pretty accurate reverse bias breakdown voltage. They are used "backwards" in circuit in comparison with the common diode.
Excellent videos!!! I was wondering if you might be able to explain how U1 generates the 10.2 VDC output a bit better. I have two of these kits and neither of them works. I don't understand how no input on pins 2 & 3 can initially generate the 10.2 volt output. The rest of the circuit I do (mostly) understand. Thanks a million!!! Keep the good vids coming!! Kenny
I built one of these about 3 years ago and it's sat in my drawer until a couple of days ago - it's the unbranded variety but identical to yours. Now I'm just trying to figure out the best wattage linear transformer to shove 24 volts into it.
Nice! And it uses all off-the-shelf parts. One thing I notice on the schematic is the auxiliary negative voltage to be able to adjust the minimum output to 0V. This can be a nuisance that if done wrong can make your output voltage fluctuate up and down at the moment you turn off the power supply. I had the experience with an Elektor magazine circuit that used an op-amp and a -5v auxiliary supply to drive an L200 regulator, and when set to some voltage, lets say 9V, at the moment of turning off the supply, the power part and the auxiliary part discharged at different rates, and this made the output jump from the 9v I had set, to 12 or more volts for a moment and then down to 0 as it all got fully discharged. Finally I powered the opamp with single supply, not using the -5v auxiliary, and the circuit lost its feature of going down to 0, but the weavy jumpy voltage problem at switch-off disappeared.
Can this module be increased in output to around 45 volts, current unchanged. A 15 volt zener in the earth of the regulator chip may do the trick? With a suitable XFMR of course.
That design (first published in some German magazine years ago) suffers from overshoot on powerup, unsuitable opamps for the stated voltage range etc. There is a thread on EEVBlog forum about it, various people tried to fix it. Forgot to add, anyone looking to buy this kit, you can get it a AliExpress for $3.65 including shipping. So with all of it's flaws you can't beat that price.
One of those threads is mine. I modded the board to improve it but still ended up downgrading it to 2.25A at 16V max. Seems to work ok with the mods at this reduced capacity.
This is a "chinese type kit" Comes without assembly instructions, schematic, theory of operation. You gave to guess a lot during assembly. #$&* ! Remember Heathkit.
Please be advised that there are "fakes" out there... EBAY, etc. The genuine ones, like this, will have the voltage regulator for the fan in the upper left corner: It will be parallel to the edge of the board. On the fake ones, the voltage regulator will be perpendicular to the edge of the board. Also, the drive transistor will not be located on the edge of the board.
I realize this is a 2+ year old video; however, I do have a quick question. I have a 24VAC transformer, (2 wires on out). Do I wire it up like you do? (I have the same kit). I have noticed some people have a 12-0-12 AC Transformer, and they use all 3 terminals on the board from the 12-0-12 transformer.. This is my first kit involving AC Transformers. (I do understand them a wee but; but, I'm still learning.) I have watched countless videos on this kit. You are a great teacher. "AC doesn't matter which way" I say to that comment; Thank you, that is good to know. The input side is different, as I already understand that. Thank you for a reply (in advance). ~J
I found the oldest and probably the original circuit and description in PRACTICAL ELECTRONICS October 1978 page 1070: worldradiohistory.com/UK/Practical-Electronics/70s/Practical-Electronics-1978-10.pdf There is a good description of the circuit operation.
