I’ve updated my PIC multiplier with a 4-layer PCB and optimized the layout to minimize the board area as well as make the surface mount components easier to place.
This circuit, based upon the DC Signal Multiplier outputs a PWM signal with a duty cycle which is calculated from two protected DC analog input signals. The PWM signal output power is bolstered with a MCP1416, with PPTC overcurrent protection.
PIC Software for Multiplier:
Thought I’d share my approach to protecting analog and low frequenct signal inputs to sensitive electronics:
I developed this circuit to gather average voltage and current data for a switched DC load and serve them as 5Vmax analog outputs as well as use them to produce a 5Vmax analog signal representing the power. In addition to these analog signals, there is also a resettable instantaneous over-current relay output. Current flow must be from Load(+) to Load(-) for proper operation. The PIC_Multiplier is this. This circuit is used here.
Bill of Materials:
While considering making a constant power DC power supply, I realized that it was quite challenging to come up with a way to multiply DC analog signals. I eventually decided that it’s simply much cheaper and easier to go ahead and use a microcontroller. In this case, a PIC10F322. RA0 and RA2 are used as ADC inputs, and RA1 is used as a PWM output which is passed through a low pass filter to convert it into an analog signal. Finally, RA3 is used to reset the controller if supply voltage drops below an acceptable threshold.
Circuit board design files:
Microchip MPLAB X microprocessor programming files for this device: