I have a 6v DC motor that controls a physical system similar to a window blind, using one SPDT toggle switch and two SPDT microswitches for control. I have seen similar setups with hoists, however I do not know if the toggle switch was SPDT or DPDT.

Ideally: A SPDT toggle switch will determine if the blind is to be up or down, reversing the polarity on the motor accordingly. One SPDT microswitch determines when the blind is fully up (And halts the motor when the toggle switch is in the up position). Another SPDT microswitch determines when the blind is fully down (and halts the motor when the toggle switch is in the down position).

Using just those three SPDT switches, is it possible to achieve the above result? I can't work out how to formulate this mathematically. Without maths, the best I have come up with needs a DPDT toggle switch, as follows:

![schematic](https://i.stack.imgur.com/vrSSo.png)

[simulate this circuit](/plugins/schematics?image=http%3a%2f%2fi.stack.imgur.com%2fvrSSo.png) – Schematic created using [CircuitLab](https://www.circuitlab.com/)

The next idea for a solution would be to use an H-bridge BJT circuit, perhaps with some logic or a low-end 12-series PIC microcontroller.

Any solutions would be helpful. (As a bonus, I'd be very interested in the maths which confirms if a solution with just three SPDT switches would be possible, and what the circuit would be)

Thanks