When you need to connect you gear to unknown source then you risk to blow your radio. This small circuit I designed to be very cheap. This tester you connect first to unknown powerpole connector and test polarity and voltage level. If anything going wrong then you just blow your cheep tester and not your expensive radio.
When you connect powerpole tester to unknown powerpole connector then first check polarity, if polarity is wrong then flash red colour led, if polarity is right then check voltage level. Dependent of voltage level different colour glowing a bi-colour LED.
Default Voltage Levels:
Green >11.5V - <15V
You can change voltage levels if you want in microcontroller source code.
Step 1: Schematic
Input connector and Power Supply
CONN1 is a input connector. From CONN1 connector get power a circuit and as well measure input voltage. Input D1 - D4 diode's are connected in Gratze bridge, this is important to we have always correct polarity power supply to the circuit. Power supply is standard 78L05 IC and couple capacitor.
R1 and R2 divide input voltage to A/D working voltage range. In this resistor setup you can use till 20V. If you need higher or lower input voltage range, you need to recalculate R1 and R2 value.
PIC12F675 - A/D Converter, Comparator, LED Driver
In PIC running the Anderson Powerpole Polarity and Voltage Tester software. The software is written in JAL programing language. First read A/D converter, after compare A/D value with user defined comparator toggle levels and finally pull down to GND LED's Cathode.
"Display" Bi-color Led
Whit one bi-color led you can read status of the comparator.
Default Comparator Trigger Levels and led colors:
Low Voltage (Amber/Orange Led) - <11.5V
In Range (Green Led) - >11.5V - <15V
High Voltage (Red Led) - >15V
Wrong Polarity - Flashing Red Led
Step 2: PCB
I designed small PCB for Anderson Powepole Polarity and Voltage Checker. The PCB size is 50mm by 25mm (approximately 2” x 1”). You can download pdf file so you can make yours own pcb.
I made my prototype PCB with toner transfer method. If you are interested in future I planing to make PCB and kit for sale. Contact me if you want kit or PCB.
PCB Soldering Steps:
1st. Solder in the wire bridge (Red line on picture. Between U2 and CONN2)
2nd. Solder in the diodes.
3rd Solder in the resistors
4th Solder in the capacitors
5th Solder in the ICs.
6th Solder in the LED(to the square pad need to orient flat side of led) and programming header.
R1 - 30 kOhm
R2,R3 - 10 kOhm
R4,R5 - 470 Ohm
C1,C4 - 10 uF / 25V
C2,C3 - 100nF
D1,D2,D3,D4 - 1N4148
LED1 - Bi – Colour Red/Green LED (Common Anode)
IC1 - 78L05
IC2 - PIC12F675
CONN1 - Red and Back Anderson Powerpole connector shell and 2x 15 amp pin, or screw terminal connector.
CONN2 - 6 pin header
Step 3: Source Code and Programming PIC.
Don't forget to read out and save the oscillator calibration value for your PIC. If you using Pickit2 or Pickit3 programmer then you don't need to care for calibration value. Programmer software will handle for you. Just if you using non Microchip written program then you need too do this.
The source code is written in JAL2 programming language. You can download from here the source code and hex files.
How callibrate my Anderson Poverpole Polarity and Voltage Tester?
You need to modify ad_variable.jal file.
Line 24 - const dword ad_conversion_variable – You need to recalculate this value if you changing R1 and/or R2 resistor's or you want to calibrate for your exact resistor value.. From line 17 – 23 explain calibration calculation steps.
Line 34 - const dword ad_ground_offset_value = 7000 - You need to add ground offset voltage value. From line 27 - 33 explain how calculate ground offset steps.
Line 43 - const byte under_voltage = 115 – You need to ad your under voltage threshold voltage value. You need to write in without comma or full stop. Example 11.5 Volt need to be 115.
Line 46 - const byte over_voltage = 150 – You need to ad your over voltage threshold voltage value. You need to write in without comma or full stop. Example 15.0 Volt need to be 150.
Plug your PICKIT2 or simular programmer to CONN2 header and download main.hex file to board.