How to use a DPDT switch and a NC switch to control the direction of a motor?

[theruss007]

If you go to Instructables - Make, How To, and DIY and type: the worlds most useless machine, you will see what a want to acomplish.There are two ways to build it, a 555 timer servo controler or a DPDT and Normally Closed bumper switch. I want to use the second option because it is easier. It doesn't give a schematic just a bad diagram of the circuit. . I understand how the DPDT switch turns the motor one way or another but how does the bumper switch work in that circuit. Sorry if this may seem stupid but I just dont want any accidental short circuits.

 

[Gary B]

Put the SPST in series with the withdraw power feed to the motor. When the hand is fully retracted, it opens the switch. When the hand moves forward, it trips the switch to the closed position as it moves to flip the reverse switch back to the withdraw position.

 

[ghostman11]

my first reaction was why!!!! what possiable use was it. but i have to admit i wouldnt mind one myself

 

[theruss007]

Thank you. I am sure if I thought about long and hard I would have figured it out, but still I could have made a mistake.

 

[mgeno216]

Hey I am building the samething. I am also a member at instructables, so if you want I will email you the full instructable. The way without the 555 is easier. It took me a while to understand exactly what they were saying so I will try my best.

The way I saw is you take your DPDT switch and wire it like this
**broken link removed**
The blue lines are wire.

So how this works:
I assumed you modded your servo to spin continuously. When you apply power to the posistive lead of the servo, it spins forward. When you apply power to the negative lead of the servo, it spins backwards. What the DPDT switch does is select which way the motor spins. When you push the switch on (like pushing to switch to the right in picture) you connect the battery + to the motor + and the battery - to the motor -. The moves the motor forward. The motor will spin the arm out of the case and push the switch back. This moves the switch to the other side. Since the SPST switch is noramlly closed, the current will be reversed (battery - to motor +, and battery + to motor -). The arm will start moving back in until it hits the SPST switch. When it does, the switch will open allowing no current to pass to the motor. That completes the cycle, It will now wait for the switch to be pressed again.

In the picture the right side of the DPDT would be labled off and the left side would be labled on.

I did my best a explaining it, but it is a little hard to explain.

Good Luck

Mike

 

[ghostman11]

awwww now i am going to have to build it!!! its the kind of useless totaly pointless waste of time and effort sort of thing that i would love on my desk lol

 

[mgeno216]

It is very simple, and hilarious. I first saw this on the Colbet Report and watched it probley 5 times and couldn't stop laughing

 

[theruss007]

wow! me too I love watching the Report. When I saw it I only saw the last part of the interview. Then the next day by chance I saw it on instructables.

 

[mgeno216]

Did my explanation help. It is hard to explain.

Mike

 

[theruss007]

Yes it did. My only question is :Is every DPDT going to have the same pins in the same position. So I can use it as a reference.

 

[mgeno216]

Yes I think so. I got mine at Radioshack.

Radioshack
DPDT Heavy-Duty Toggle Switch with On/Off Label Plate - RadioShack.com

Digikey
Digi-Key - 450-1533-ND (Manufacturer - A201SYZQ04)

Maplin
**broken link removed**

All of those would work. For the DPDT just make sure the setup is on-on

Mike

 

[theruss007]

Thanks to everyone. I will most likely get mine at Radio Shack, but they have a limited parts list though. Thanks again.