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I'm building DC motor blind movement. I've paired motor with bi-directional PWM controller but so far I need to stop/start manually or time it...temporary I have USB relay configured to open blinds every morning. I'd like to add some automatic stop position circuit.

First I've been tinkering with magnetic/reed switches (3 contacts), but I've smashed those delicate glass tubes in the process. Plus, they were switching reliable only 2-4 cm from neodym magnet. Now I'm thinking about voltage comparator with IR led transmitter & receiver and some reflexive sticker/paint to mark my end positions. The circuits I've found is outputting logic signal, but probably I could connect that to small 5V dc relay to shut down the motor (12 volts). But with these I'll need to put up something like 8 wires. Or maybe less if I'll use diodes & step-down regulator to supply stop circuit.

Any thoughts/ideas, how to solve this better? I might end-up with some arduino at the end, but I wanted to do this "the old way" first

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  • \$\begingroup\$ The reed switch like this one \$\endgroup\$ – czechDude Apr 12 '17 at 13:45
  • \$\begingroup\$ Put your comments into your question. \$\endgroup\$ – 12Lappie Apr 12 '17 at 13:51
  • \$\begingroup\$ as a newbie i can have only two links in question :/ \$\endgroup\$ – czechDude Apr 12 '17 at 14:01
  • \$\begingroup\$ WHat does the mechanical setup look like... can you add a drawing \$\endgroup\$ – Trevor_G Apr 12 '17 at 14:42
  • \$\begingroup\$ I would personally use a stepper motor and control the number of steps it takes to move the blind a certain distance. \$\endgroup\$ – 12Lappie Apr 12 '17 at 15:11
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This type of thing is usually handled with a traveller arrangement like the flowing.

Motor rotates a screw with a threaded traveller (Restrained nut). Two micro-switches are positioned where you want the power to be cut.

Usually either the position of the switches is made adjustable with slotted holes for clamping screws, or two nuts are used and rotated to the appropriate offsets with the restrainer removed.

enter image description here

The switches are then wired to disable the appropriate drive direction.

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