# Trying to build a motor control circuit with discrete input for position control

#### Zoomie13

Joined Aug 27, 2006
2
Hello all!

I have a Denso 12V motor (p/n 063700-1544) that I'm trying to use for a temperature control driver. At the moment, I can use an available Toshiba TA8050P motor driver chip and a 3 position switch to drive the motor fwd/off/rev. Full sweep, the motor drives thru 90 degrees.

However, I'd like a more elegant solution using a rotary switch that has 15 discrete positions. I'd like this circuit to be as simple as possible; it will be driven by a 12V power supply.

Attached is a scan of the motor drive circuit board: (the attached wiring is listed 1 thru 5 at the image bottom. 1 and 2 are the motor leads. 3, 4, and 5 provide resistive feedback. At full sweep one way, there is 4.8kOhms between 3 and 4 and 1.45kOhms between 3 and 5. A 90 degree full sweep the other way, there is 1.3kOhms 3 to 4, and 4.9kOhms 3 to 5. The resistance varies linearly between these extremes).
I'll list the switch logic in the next post...

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#### Zoomie13

Joined Aug 27, 2006
2
Continuing...

The rotary switch I'd like to use has 5 leads: A, B, C, D, and common. The following grid shows the 15 discrete positions available:

1___A
2___A_B
3_____B
4_____B_C
5___A_B_C
6___A___C
7_______C
8_______C_D
9___A___C_D
10__A_B_C_D
11____B_C_D
12____B___D
13__A_B___D
14__A_____D
15________D

Can anybody help me find a simple, elegant, solution to this problem?

Thanks!

#### Søren

Joined Sep 2, 2006
472
Hi,

However, I'd like a more elegant solution using a rotary switch that has 15 discrete positions. I'd like this circuit to be as simple as possible
Use a normal rotary switch, or you'll have to use a D/A-C (or an A/D-C if used another way).

Connect resistors of appropriate value to each switch position and use a comparator (with a bit of hysteresis to avoid hunting) to compare the resistance of the switch with the resistance from the motor gizmo, add a buffer/driver and Bob's your uncle.