Well mad scientist in me wants to try it. I bought small circuit from company RLS here in Slovenia. It is incremental encoder circuit with NPN open collector outputs. It works with small polarised magnet that rotates in the end of a shaft.
I decided on NPN open collector output because my interface has to receive square weave voltage to count. So i decided i will put pullups to A, B and Z signals to make direct access to chip.
Biggest trouble i expect with getting sensor into center. Magnet is no trouble. I made a shaft doubler with M12 x 1,25 (fine pitch) on one end and small bore for 4mm magnet on the other. This doubler will bolt on rear end of the shaft and magnet will spin in center. No trouble for a lathe..
But mounting PCB proved problematic. How to mount round part on center shaft using rectangle mounting.
I will try to copy resolver casing in aluminum and use four mounting bolts to position PCB over shaft in center.
A friend lent me his milling machine and we leveled motor back cover. It is now good to accept somewhat higher mount in order to attach RLS sensor. We reviewed couple of options to mount encoder disk.
I am in fauvor of second option, since it will allow me to use the same hardware and mount the cables in the same way.
A friend got the fitting made and i tried it on motor. It is made exactly as original resolver fitting with different center mounting for encoder.
I put encoder plate on.
I had to make a small fitting for sensor magnet. It has to spin in center of axis within 0,1mm and it has to be cca 0.1mm from lower side of the plate.
First I made a 10.2mm hole in a 20mm piece. I used M12 x 1.25 tap bit to make threads on the inside. When i had the distance of threads i screwed the thread bit in and centered whole thing on my lathe. Mind you because of uneven slope of my hand threading whole piece was off center. But i didnt mind, since i turned the piece and made it round and center with some 18mm diameter. Then i made a small circle of 12mm and 16mm underneath. I took the piece from lathe and put it in the mill. I made side indentations for 14mm wrench and i made 13mm hex form on the upper part. That way i can efficiently torque the piece on motor shaft.
I glued magnet in with Loctite 638 compound for fitting cylindrical parts.
I put some coloured wires on sensor plate. Red (+5V) and gray (gnd) White (B), Yellow (A) and Orange (Z)
Since encoder is open collector output, i had to add pullup resistors to input lines, so that they would invert reading. i fixed one 4K7 ohm resistor leg to unused hole for +5V pickup and soldered others so they are not in the way of each other. Now when i switch inverter on i get +5V on the A, B and Z lines. Encoder will now change states from 0 to 5V.
Aleš made a fitting for sense magnet according to my design, bit his tools are better and end product is prettier. Notice slit body and Allen bolt on the side. It is designed so it can be adjusted in height up to the encoder mount and then bolt brings threads higher in effect locking the fitting on shaft.
leafdriveblog 