It has been a while but i finally started on the programmable part of my dc load and in this topic I will post my progress and questions.
Old topic:
https://www.eevblog.com/forum/projects/did-i-forget-anything-constant-current-load/Basic idea:Cypress Psoc 5Lp + dc load = Programmable dc load
I already made most of the processor part of the design:
Schematic(pcb is not done):
https://dl.dropboxusercontent.com/u/100819959/DCDCTESTER/dcdc_tester.pdfThe board has:Psoc 5LP - 20bit delta sig adc , 2x 12bit SAR adc , rtc ,full speed usb ...
http://www.cypress.com/?docID=428823.3V and 5V ultra low noise ldo's
http://www.ti.com/product/lp38798128x64 Newhaven GLCD
Micro SD card socket
High resolution ALPS rotary encoder
Things that I will add:Support for multiple temperature sensors (thermistors or somthing like LM35 ...)
External high resolution dac
The load stuff
The current measurement stuff
As Dave has explained in his dummy load video you can have a :
-Pulse load
-constant current load
-constant resistance load
-constant voltage load
And test / plot a lot of cool things
I also incorporated input voltage and current measurement so you can test / plot the efficacy of linear / dc-dc converters over load.
And it measures the output/load voltage so it can also do low voltage cutoff to protect batteries under test.
My basic design for the input measurement:And for the load:TODO:-Determine which external dac to use
-Determine the best opamp for this situation (adc buffer , voltage follower for mosfet etc..)
-Use IC1 (INA168) yes or no
-Adc / DAC Input/output protection
-Reverse voltage protection
-Overvoltage protection
-Power INA168 externally (problem when DUT < 2.7V)
...
I would like to have your help to select the components to use and other things to implement in the design.
Thanks!