Electronics > Projects, Designs, and Technical Stuff
DIY Modular Test Equipment Project
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void_error:
The User Interface schematic is almost finished but I thought I'd ask for a few more opinions before I call it finished.
A few component values still have to be calculated.

Mastrofski:

--- Quote from: SaabFAN on June 04, 2016, 12:59:36 am ---
--- Quote from: TiN on June 03, 2016, 01:50:00 am ---Subbed.

I'd suggest 14-bit DAC for DC load. That will allow to set current in 1mA steps with some wiggle for calibration. Sometimes it's nice to have.
Or at least two ranges (low current, high current) like in some production DC loads. ;)

--- End quote ---

Just a little note here: Using old components bought on ebay, or from Grandpas part-box is often really worth it.
I have an almost finished (Haven't built a case yet) DC-Load flying around somewhere that uses a Ferranti 8-Bit DAC, a 4066 to switch between 2 current-ranges and an LM324 as the controlling Op-Amp on a Euro-Card. It's quite a mess because of the parallel data-bus, but you can debug the circuit with a Multimeter instead of a digital scope with Serial Bus-Decoding.
Also it looks kinda cool having some ceramic DIP-Package with a golden cap on it :)
And you can build it on Vero-Board in an afternoon instead of waiting for 3 weeks until the boards arrive.

--- End quote ---

I think for one-off pieces of equipment, using odds and ends is fine, but for something going into production, or something designed to be recreated by others(such as this project), sourcing components begins to become an issue.

Love the idea though! I'll definitely be following along.
timofonic:
Amazing project!! Are you going to release as Open Hardware and Open Software at GitHub?

There's already a lab power supply project. Maybe a colaboraron would be possible of some kind.


Thanks.
void_error:

--- Quote from: timofonic on June 05, 2016, 04:59:26 am ---Amazing project!! Are you going to release as Open Hardware and Open Software at GitHub?

There's already a lab power supply project. Maybe a colaboraron would be possible of some kind.


Thanks.

--- End quote ---
You mean this?
Not sure yet if I'm going to make it open source, will decide after I build it.

I still have to make some changes, thinking of moving the USB micro of the UI to a separate board and have an off-board connector for UART. USB connectivity was something I don't plan to add before I have the UI board built and tested and I'll need some separate USB-UART modules anyway.
void_error:
If you're all wondering why I didn't use a SPI connection directly to the LCD and instead went for I/O expanders it's because SPI doesn't allow reading the LCD data (see UC1701 datasheet) such as BUSY status.

Modifications to the Waveform Generator have been completed, it's now time to switch from I2C I/O expanders to SPI ones for the UI as the Waveform Generator already contains one.
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