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Help re: Sensor/Switch reversing DC motor project

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drovers

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Hi
Foolishly I have volunteered to take on a "little" project for our target shooting club in Worcester UK.

I thought I could "Easily" come up with a simple fool proof circuit to do the following,(However, its now really bugging me, and I'm ashamed to be asking for help now as I've found this more involved than I originally thought. Physical electric motor/pulleys are simple for me. It's the electronic control circuit that I'm failing on!

Goal:-

To create a 12V DC electric circuit that has 2 switches/sensors at either end of a 20 meter rail that will send a carriage backwards and forwards when the carriage reaches the end of the 20 meter linear track/rail.
The idea being that this carriage holds a Shooting Target that constantly moves right to left, hits the end of the 20 m rail activates a sensors/switch that reverses it direction until it hits the other end sensor /switch, and then reverses the carriages direction etc.
Any help would be greatly received.
The goal being a simple idiot basic circuit design any advice would be greatly appreciated.

I really would be grateful for any help.
I was trying to do this with latching switches, but realized this would not work as the RHS end would have to reset the LHS end and vise- Vera, and this is where it all went horribly wrong for me!
If you require a donation to a worthy charity I would be more than grateful to oblige!

Many many thanks

Mike.:confused:
 
Hi

I was thinking about this, and i recon that you could build this using just a single relay and 2 switches.

please excuse the really crap drawing, but i cant find any of the symbols in my cad library.

The relay would need to be a 3 pole changeover, possibly https://uk.farnell.com/jsp/Electric...6283-9012-0000/displayProduct.jsp?sku=1169285

and 2 switches, 1 switch needs to be n/o and the other n/c, or you could just use 2 changeover switches, and wire them accordingly.

i choose a faston style relay, because i think the circuit could be hardwired to the relay, therefore no pcb, or anything else required, just some wire and a few faston terminals.

The switch on the RIGHT(R) hand side is N/O, and the LEFT(L) side is normally close.

Circuit operation,

when powered up, the motor will turn to the right, when it hits the RIGHT limit switch, the relay coil will energise, and latch (via the 3rd pole).

When the relay energises, it will reverse the currnet to the motor, causing it to run anti-clockwise.

When the LEFT limit switch is reached, it will break the power to the coil, causing the circuit to reset, and start heading clockwise again.

(please note, this is off the top of my head so please double check my logic before ordering parts if you use this circuit)

If needed i can draw a diagram complete with pin numbers for the relay to make wiring easy.

Hope this helps

Graham
 

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drovers said:

Hi Mike! Welcome to the board!

Goal:-

To create a 12V DC electric circuit that has 2 switches/sensors at either end of a 20 meter rail that will send a carriage backwards and forwards when the carriage reaches the end of the 20 meter linear track/rail.
The idea being that this carriage holds a Shooting Target that constantly moves right to left, hits the end of the 20 m rail activates a sensors/switch that reverses it direction until it hits the other end sensor /switch, and then reverses the carriages direction etc.

I think you were very close to the answer. Near as I can figure you can do this with just two DPDT switches (such as guitar stomp-box switches) wired in polarity-reverse. The motor will always reverse direction when one of the switches is flipped. It doesn't matter what orientation either switch is in to start with; as soon as the target hits one of the switches and flips it, the polarity to the motor will reverse and the target will go the other way until it hits the other switch. . .etc.


Hope this helps!

Torben
 

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Torben said:
Hi Mike! Welcome to the board!



I think you were very close to the answer. Near as I can figure you can do this with just two DPDT switches (such as guitar stomp-box switches) wired in polarity-reverse. The motor will always reverse direction when one of the switches is flipped. It doesn't matter what orientation either switch is in to start with; as soon as the target hits one of the switches and flips it, the polarity to the motor will reverse and the target will go the other way until it hits the other switch. . .etc.


Hope this helps!

Torben

thats nice neat and simple, kinda like the wiring for stair lights, dont matter which one you press.

EDIT: just had a quick thing about this, the difference between the two circuits would be the pressure required on the switches, on Torben's design the swiches would need to be bigger to handle the current for the motor (which would be no problem in the specified scenario). I think my circuit might be useful to people looking for a circuit for making a model train (electric) traverse back and forth along a track as you can use very light duty switches, like mikro switches or quite possibly reed switches, so there is no physical contact with the body being moved.
 
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Wow!
Really big thanks to you Guys, Wmmullaney, Weegee and Torben. I'd really played with this and everything I came up with was just getting bigger and bigger and just too complicated!
I'm going to try Torbens first, as you say nice neat and simple,
Many many thanks
When it's built I'll PM / Post abit of video, plus let you know when we've
got an open day- (If your in the UK!)... you can let loose with some rounds a "your" moving targets!
https://wnsc.co.uk/
Many thanks again
Kind regards

Mike
 
weegee said:
EDIT: just had a quick thing about this, the difference between the two circuits would be the pressure required on the switches, on Torben's design the swiches would need to be bigger to handle the current for the motor (which would be no problem in the specified scenario). I think my circuit might be useful to people looking for a circuit for making a model train (electric) traverse back and forth along a track as you can use very light duty switches, like mikro switches or quite possibly reed switches, so there is no physical contact with the body being moved.

If the amperage required by the motor is strong enough to require high-amp switches, I would think the motor would be capable of triggering those switches.


Torben

[Edit: I just re-read that and realized that's not at all what you meant. Please disregard this post as the result of sleep deprivation.]
 
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drovers said:
Wow!
Really big thanks to you Guys, Wmmullaney, Weegee and Torben. I'd really played with this and everything I came up with was just getting bigger and bigger and just too complicated!
I'm going to try Torbens first, as you say nice neat and simple,
Many many thanks
When it's built I'll PM / Post abit of video, plus let you know when we've
got an open day- (If your in the UK!)... you can let loose with some rounds a "your" moving targets!
https://wnsc.co.uk/
Many thanks again
Kind regards

Mike

Hey Mike,

I'm looking forward to hearing how it works out. One thing that occurred to me: in order to extend the life of your switches, you might want to include something called an "RC snubber" across the motor. This is just one resistor and one capacitor in series from one motor terminal to the other, and helps to keep the motor's back EMF spikes from causing the switch contacts to arc. See the amended attachment.

I'd try maybe a 0.1uF cap and 100:eek:hm: 0.5 Watt resistor to start with.


Torben

[Edit: Make sure you use a non-polarized cap!]
 

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iam a finalist in Electrical Engineering am given a task to design an
electronic circuit of an Automatic Processed Rubber cutter which cut rubber
in a specific legth for tyre construction.Suggest me a circuit diagram and
mechanism.My IDEA,i think there will be a processed rubber moving along the
conveyor belt and i will have two light sensor pisitioned a distance between
the two equal to the legth of the rubber to be cut.so when both of the
sensor are covered by the rubber the Power saw will be actuated and cutting
is made at the left most sensor,Then the rubber will be removed and all the
sensors will again face the light again as the result the power saw will
stop and the auxiliary contact will inform the belt to proceed.CAN THAT BE
POSSIBLE???My brother am from East Africa !I need your support!God Bless you
 
dovers,

This should work for you . Start, CW Limit, and CCW Limit are all momentary NO switches. Stop is a momentary NC switch.

Ken
 

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im a beginner trying to build a simmilar project, but on a smaller scale. the main differences are: push a button (momentarily) to make the target move away till it makes contact with a switch at the far end of the range. then when you feel like it, press the the same switch again to move the target back towards you until it makes contact with a switch at the shooters end of the range. the mechanism requires that the motor turns in one direction to move the target away, and turns in the oposite direction to bring it closer.

this is the catch - it isnt actually gonna be used in a shooting range. thats just the basic concept of the circuit i need help with. its gonna be used to raise and lower a motorcycle numberplate so it needs to be as small as possible and operate from 12v dc.

the mechanism i have built is simple, but it is almost impossible to describe. i can mail a pic to anyone willing to help. any help will be apreciated :)
 
dovers,

This should work for you . Start, CW Limit, and CCW Limit are all momentary NO switches. Stop is a momentary NC switch.

Ken

Mia Colpa! My motor reverser circuit (above) Does Not WorK! :(

Thanks, saturn1bguy, for catching that. No more mental circuits. I was trying several things at once and sort of got lost in it.

Ken
 
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