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US-Digital MA3-P12

The MA3-P12 from US-Digital is available for about AUS$35 plus exorbitant postage. This small 'potentiometer look alike' device uses a AS5045 or similar device to produce a PWM output.

The device interfaces directly to an AZ/EL board but uses the new program for the 16F628A called PWMunit.hex

This is a very economical rotary encoder with an accuracy of better than +/-0.5 degrees. The device outputs PWM and I now have the hex code for a 16F628 or 16F648A working in the AZ/EL unit. The US Digital encoder connects to pins 1 (+5V), 2 (earth), 4 (PWM in) of the encoder connector on the AZ/EL unit.

I have produced a separate manual to go with the source code.

The MA2-P12 is an ideal solution for satellite users and EME enthusiasts with beamwidths of the order of a degree. I have reprogrammed the switches as follows: SW1 180 degree shift in readout, SW2 if on sends ASCII to a terminal unit rather than the shack unit, SW3 reverse direction. Here is the hex code for the AZ/EL unit's PIC16F628/A or 16F648A. It accesses the pulse width modulated output of US Digital's MA3-P12. Here is the manual to describe how to get it going. I suspect the active unit inside the MA3-12P is an AS5045.

I recommend that if you buy one of these units that you also buy the plugs prewired. They are very tiny and not what I call fun to connect.

A US-0Digital MA3-P12 connected to an AZ/EL board.

Top of rotator.jpg

Colin VK5DK mounted an MA3-P12 in the top of a Ham 11 rotator after removing the wire wound pot. The AZ/EL unit mounted nicely in the side of the rotator system and as you can see it fits quite well.

Colin uses it to point his 10Ghz terrestial system as the potentiometer in Ham 11 was not accurate..

He uses the VK5DJ rotator system in single input mode for Azimuth only.