Lab PSU 0-30V /10A – Part 12

The good thing about a blog is that it is excellent for notes – if I make my work-notes here they are called “documentation” 🙂

The following are programming notes for the PSU Control Board:

PA10 – GPIO J1-4 Relay 1 – Connect extra 12V – 36V If Relay 2 is On.
PA9 – GPIO J1-5 Relay 2 – Connect extra 12V – 24V
PB1 – GPIO J1-6 Relay 3 – Switch On/Off Output from regulator.
PA7 – ADC J1-7 Temperature 3
PA6 – ADC J1-8 Temperature 2
PA5 – ADC J1-9 Temperature 1
PA4 – GPIO J1-10 Fan 3
PA3 – UART1 J1-11 RX
PA2 – UART1 J1-12 TX
PA1 – ADC J1-13 V Out. Measure Out Voltage in a split 10:1
PA0 – ADC J1-14 CSense Out. Measure Voltage in a split 10:1 before current shunt. CSense – V Out = shunt voltage.

Current Out = Shunt Voltage / (0.47R / 2)

PF0 – GPIO J2-6 Fan 2
PF1 – GPIO J2-7 Fan 1

Note 1: A 12 bit ADC scaled for 30V (30/4096) will detect ca 7mV changes in voltage drop over the shunt. Given a shunt resistor of 0.235 Ohm (0.007V / 0.235R) that gives a resolution on ca 31mA on the current calculations. This is a little less than I hoped for, but the alternative is to use an external current sensor to increase accuracy – I need to work on this a bit.

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