The Scullcom DC Load project - Page 1
Forum section: electronics / projects

author: nikifena
author_rank: Regular Contributor
timestamp: July 04, 2017, 08:14:46 pm
content: Hi there. I'm working on a Louis DC load project for few days. Still arranging the PCB and the schematics. I added a Li-ion battery management circuit.My idea is to put the entire project on one PCB. The mainboard has the LCD, the buttons, the rotary encoder, two small buttons for the load on/off and for power.I'm not ready yet, but this is the current design I have made.For the charger and DC boost, I use all in one Chinese chip. If there are any better alternatives, please tell meI added capabilities to power this device from a transformer or to charge a battery inside. So in both ways, one part of the supply ( 7805 regulator or Li-ion supply) must be omitted.NikiPS: The Louis youtube channel including video explanation about his project is here:https://www.youtube.com/channel/UCDqryeq1kMDSEQwltWqASrA/videos

author: floobydust
author_rank: Super Contributor
timestamp: July 04, 2017, 08:27:44 pm
content: Can you give some specs without having to watch a youtube video?Where does this mysterious -VCC node for the output stage go?I don't see any SOA protection so I give it a meh rating.

author: nikifena
author_rank: Regular Contributor
timestamp: July 04, 2017, 09:01:08 pm
content: As I told you. I'm not complete with the entire schematics yet. I will add the negative supply soon.Still arranging the PCB and the schematics.

author: sanman
author_rank: Contributor
timestamp: July 05, 2017, 04:06:34 pm
content: it is good that you are consolidating all of his revisions into a single PCB. I felt this project got a little convoluted as he started adding as the project moved along.It would be fun to build with a proper PCB in place.

author: nikifena
author_rank: Regular Contributor
timestamp: July 14, 2017, 02:15:37 pm
content: I tried to contact with Louis. Unfortunately still waiting for his answer.Anyway. I'm almost done with the entire design.If you can see the current version, use acrobat reader only to open the PDF file:https://www.docdroid.net/C4w6h2h/dc-load.pdfNiki

author: Mechatrommer
author_rank: Super Contributor
timestamp: July 14, 2017, 05:44:39 pm
content: Quote from: floobydust on July 04, 2017, 08:27:44 pmstudying the latest provided Louis' schematics... he's using 4x BUK956R1-100E, thats 120A rated each, so probably 480A rated at 100% capacity, or 240A with 2x safety factor, or 120A at quarter capacity, and so on and on... and then if basing on his shunt resistor and ADC choosing, if MCP3426 gain is one, 5V will be sensible on the 0.1ohm shunt, that is... 50A capacity, so almost 10x safety factor. but if MCP3426 gain is 2, then half the current twice the safety factor, finally if gain is 8, thats 6.25A, 80x safety factor. at 50V input, thats more than 300W of heat discharge, then again, it will depend on how good his heatsinking is... otherwise it will trip (load cut off) so frequently...Quote from: floobydust on July 04, 2017, 08:27:44 pmfrom U13 ICL7660 negative volt generator in psu section (this new thing i just learnt, but...)http://www.intersil.com/content/dam/Intersil/documents/icl7/icl7660.pdfat 20mA it will sag up to -4V (from -5V no load condition) maybe his whole circuitry to -ve rail source alot less than that hopefully.Quote from: floobydust on July 04, 2017, 08:27:44 pmprobably its in software because the Ardruino has enough input to calculate that (Vload, temperature, Iset (set current)) what i miss in his circuit is mosfet damage detect circuitry (mosfet damage cutoff check), this can warn the user early before any further damage occured, hmmv.btw, fast forwarding his 6 parts videos, there is no load transient respond characteristic yet on DSO, only trigger characteristic (in part #6, but that still very rough and trigger does not bear any load), so we dont know how much control loop oscillation damping, overshoot, what V/us or A/us that thing capable of etc etc. maybe we can see that report from the OP when he's finish populating the complete pcb and in working prototype test stage...