AmpStrike
Forum section: electronics / projects

author: fenclu
author_rank: Regular Contributor
timestamp: April 27, 2013, 04:58:22 pm
content: HiI’ve wanted to make a lab power supply for a while now. At first it was going to be a basic, LM317 based, dual channel one. But when I saw Dave's video series on designing a PSU for the 4th time I’ve decided “Why the hell not”. Seemed like a good challenge and exercise.I started off just by adding MCU control to a simple LM317 regulator. With time came the LT3080 regulator, constant current limit etc. After a lot of changes and tweaks I’ve come up with this – the AmpStrike.Sounds fancy, doesn’t it? The project is obviously EEVBlog – inspired. It’s Open Source Hardware.From the technical point of view: it’s based on two, parallelled LT3080 to get two channels. The constant current part is basically Dave’s design. It’s based on the classic LM324 and LT1639 op-amps. The latter one has got a ten-turn trim pot next to it. It sets the gain of the LT1639. I know it’s a bit silly to put an expensive op-amp with a ten turn pot but I just happened to have two of those op-amps lying around.The brain of the project is an ATmega328 with an Arduino UNO bootloader. It’s programmed with the ICSP connector. It is accompanied by a MCP23008 I/O expander to get the I/O lines needed. As for the mixed signal circuitry: I used a MCP3424 12-bit ADC and a LTC 2655 12-bit DAC, both use I2C interface. I planned to use something more jellybean with SPI interface but I ended up gilding the lily.The output is switched by two relays. I plan to do a push button interface with two rotary encoders and a HD44780 LCD. Nothing special. I also plan to use the encoders’ switches. If you ever used BMW’s I-Drive system, you’ll know my intentions.The PCB is designed in Altium Designer. My friend’s dad was kind enough to lend me his license. I’ll have to start using something free. I plan to make my PCB with the photo positive method at home. I also plan to put a red soldermask on it with a special paint.I plan to write a basic Arduino software for it, probably with some simple menu interface.To all the haters out there: I’M A BEGINNER. I know it’s got a lot of expensive parts but the project is going to be only a one-off. It’s not designed down to a price.I’d love to make some money on it, but like I said: it’s a one-off. I would have designed it down to a price if I had the money to invest in even 10 or 20 kits. And since I live in the retarded country of Poland, Kickstarter is not an option as well. I plan to design some simple kits some time soon to finally start making some money on my electronics hobby. I have a very basic lab, I don’t even own a scope. I reckon that the best thing I can do is to make it OSHW and let the community use my design. Not that much people will build this up, it could be pretty expensive to build. I still may make some small changes in the design.The project took me about 6 months to design. Since I’m still at school I didn’t have much time recently to put into this project.If you’ve spotted some mistakes, please let me know. I’d love to know your opinion on the project. I’ll try and keep the post updated as a make my way through assembling the thing.If you’re interested, here’s my previous lab PSU :

author: Strada916
author_rank: Frequent Contributor
timestamp: April 27, 2013, 05:26:35 pm
content: You might want to read the following thread re LT3080. As it has some issues. You may need to swap it out for LM317https://www.eevblog.com/forum/projects/lt3080-wierdness-dave's-power-supply-(eev224)-gone-mad/

author: Harvs
author_rank: Super Contributor
timestamp: April 28, 2013, 10:06:28 am
content: I think you need to have a rethink about your layout. You've obviously tried to keep the digital and analog sides separate, but the chopped up ground plane wont help you at all.It's difficult to follow exactly where all the traces are going without the actual files in altium, but it looks like your differential ADC inputs are being routed to different area's of the board? You wont to be measuring the voltage directly across the output jacks and use the differential input amp that you've got in that ADC to your advantage.

author: EEVblog
author_rank: Unknown
timestamp: April 28, 2013, 11:15:58 am
content: Quote from: Strada916 on April 27, 2013, 05:26:35 pmYep, the LT3080 seems to have a nasty fault I didn't find on my other prototypes, but showed up on my latest one.Still haven't had time to investigate it though unfortunately.I'm seriously thinking to just dump it and go back to the LM317.