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.