Electronics > Projects, Designs, and Technical Stuff
DIY Modular Test Equipment Project
<< < (19/29) > >>
0xPIT:
You might be interested in this project: http://www.heise.de/ct/projekte/machmit/ctlab/wiki (German)
void_error:

--- Quote from: 0xPIT on November 13, 2016, 12:26:31 pm ---You might be interested in this project: http://www.heise.de/ct/projekte/machmit/ctlab/wiki (German)

--- End quote ---
To be honest, it would take me about a decade to build something like that on my own...
NI have done something similar but it's bloody expensive...

I never intended to put everything in the same box. Maybe I should change the title to "DIY Partially Modular Test Equipment Project"?

Anyway...
OPP circuit is working in simulation (LTspice). I used a discrete VCA and I know it has a lot of drawbacks as I played with one on a breadboard a few years ago. Since OPP doesn't have to be accurate it should be enough, limiting the maximum power to roughly 105% which is within safe limits. Hopefully this is the last thing I have to implement.
void_error:

--- Quote from: void_error on November 16, 2016, 03:28:24 pm ---OPP circuit is working in simulation (LTspice). I used a discrete VCA and I know it has a lot of drawbacks as I played with one on a breadboard a few years ago. Since OPP doesn't have to be accurate it should be enough, limiting the maximum power to roughly 105% which is within safe limits. Hopefully this is the last thing I have to implement.

--- End quote ---
And it's ditched as soon as I did a temperature sweep and expected it to be a mess and I was right.
I guess I'll have to live with some limitations for a fully analog version if anyone wants to build one...
In that case for a 2A version the load will shut down above 50V. Nothing more than a schmitt trigger needed.
void_error:
I'm thinking of changing the MCU again for something more powerful. Although the new 8-bit 16F1xxxx series has a lot of good stuff built in it might be a bit slow and lacking memory, and so far the only one I could find at Farnell and TME is the PIC16F18875 which has only 1k of RAM.
The other MCU which will be part of the control loop for the E-load, the 16F18345 is not available at the aforementioned distributors either.
EDIT: Guess I was wrong. Farnell has it.

Changing to a PIC18F would be quite pointless because I won't gain much from the 8x8 HW multiplier but the PIC24s have a 17x17bit multiplier and 32/16bit divider which is useful given the multitude of tasks it has to do.

To summarize, I'd use a PIC24FJ series 64-pin MCU in a TQFP package which will allow me to remove the shift registers on the UI board, and a PIC24F04KA201 for the E-load control loop for constant resistance / constant power loop. The other modification would be switching from SPI to UART for communication with the "smart" load modules since the 24F04K201 has only one MSSP module.They're both quite cheap.

Any thoughts on this? Let me know.
Too complicated, would take me too much time.
void_error:
The SPI isolation board is turning into a connectivity nightmare when it comes to routing. I'm limited to a width of 80mm and height of 20mm less than the DC load board which has to fit into a case which is 100mm or 115mm tall since it's going to sit on top. It'll also have to support both regular 0.1 inch pin headers as well as IDC headers. The pin headers will be used for daisy-chaining and the IDC headers only for the first board in the chain on the UI side. Daisy chaining using the pin headers also requires a mirrored pinout for right angle pin headers so this means another row of pins connected to ground.

Since the SPI isolation board also has to plug into the Lab PSU board it means that that latter has to also be 80mm wide so I guess I'll have to start working on that too to make sure everything fits together.

This is going to be tricky.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod