HELP- DC motor reverse with remote and limits

[nordic95]

Hello, Im new to this forum and was wondering if someone could help me out with a project im working on. I have a 12 volt motor that I want to control via a 2 channel remote. I purchased a controler and remote on ebay pictured. I want to use two spdt relays to control the reverse of the motor. But I also want to add in limit switches so when motor reached end of cycle it will shut down till reverse comand is givin. Can someone please show me how to wire this correctly and please be easy as Im a mechanic, not an engineer

Thanks Anthony

 

[KeepItSimpleStupid]

You need to answer a couple of questions:
1) Can the outputs be configured for toggle or momentary?
2) Do you want the operation to be:
a) push A) OPEN, Push B) Close
b) Push A toggles direction, push b) is on/off

Hopefully, it's toggle and 2a is possible.

 

[nordic95]

Good questions not sure if I can answer. Here is the descritpion off of ebay of the controller.


**broken link removed**



2 Channel momentary relay

1 x Remot Control MOMENTARY ON /OFF Relay will only stay on as long as you hold the button down.

2 X Relay output A and B

12 Volts Supply

Handles up to 10 Amps

315 Mhz Freq

Use for :

12 Volt Lighting , Solar / Marine / 12 Volt Applicatons ,

Cars , Bikes , Trucks , Motor Homes and much more




I would like to click "A" for up and it stays on till limit switch is reached. Then hit "B" for down till limit is reached. Could this be done with this controller? If this cant be done with this controller then I guess I would have to hold the button till limit is reached?

Thanks Anthony

 

[KeepItSimpleStupid]

So, you basically have to live with push button A for one direction and push button B for the other. When you release the button or hit a limit the motor stops.

But what you want may be possible.

I did forget a couple of other questions: How much current does the motor draw?

What are your constraints on the limit switch. Will a simple microswitch work for you?

Do you have any constraints on quiesent current? Meaning can it draw power when off?

 

[nordic95]

Motor draws 8 amps and yes I already have two micro switches. Basicically this motor will turn a jack to lift a portion of a boat trailer. The motor is located by the tounge of the trailer where a 12 volt battery will be mounted to power this whole project. The trailer battery will charge off the truck battery while the trailer plug is plugged into the truck. My first idea was to use the relays mounted on this controller just to control two 30amp Bosh style relays to control the reverseing and actual current of the motor.

 

[KeepItSimpleStupid]

This is a drawing I did for someone else here some time ago. Take a look at it and see if if you understand it.

The primary difference is the drawing uses two low level (+5 V) signals, UP/DOWN, but not both to activate. Basically what you want to do. Where the drawing is labeled control, it basically means a contact closure to ground. So, one or the other of the +5 volt paths would be engaged at a time. You could change that to 12.

The issue is that one relay will be on at each limit.

The limit switches do not have to pass the motor current which is a good thing.

The diode must be rated for 20 Amps or so.

The bad part is that I used DPDT relays which you can make with two of the Bosch relays in parallel or get a DPDT version.

Changing the momentary signals to steady signals can be done with a dual coil SPDT magnetic latching relay such as this one: http://search.digikey.com/us/en/products/DS1E-ML2-DC12V/255-1475-ND/465958

With a magnetic latching relay with two coils, if power is steady applied or momentary applied, the state sticks.

For now, take my word for it.

I think the circuit will oscillate if you push both at the same time. Not a big deal.

Not sure what can be done to reduce the power consumption when the system is at the ends.

See if you can understand the posted circuit and whether you can live with one relay always on. Not sure I can fix that problem.

 

[nordic95]

Yea I understand most of it, but Im not sure if its worth the trouble of getting all new equipment and more to do this. Can I just use what I already have and I may just have to hold the button? This way I can stop it at any point or till it hits the limit switch. I attached a schematic of what im thinking the momentary SPDT switch would be the two channel controller. Where would I tie in the limit switches for this?

 

[nordic95]

Here is schematic.

 

[KeepItSimpleStupid]

Much better choice.

The UP limit switch would be in series with the wire controlling the UP position near the switch. It opens when the UP limit is reached.

Ditto for the DOWN position.

You could keep the switch too if you wanted. With the one extra part (latching relay) you can convert to a momentary push.

The interface from the controller, would essentially be. Take the two Common's of both relays and tie them together and to ground.

Take the NO (Normally Open) contact of one relay and tie to UP position of switch and the NO contact of the other relay to the DOWN position of the switch.

 

[nordic95]

The interface from the controller, would essentially be. Take the two Common's of both relays and tie them together and to ground.

Take the NO (Normally Open) contact of one relay and tie to UP position of switch and the NO contact of the other relay to the DOWN position of the switch.[/QUOTE]





I dont understand what you mean by the above? Can you sketch me a diagram?

And thank you very much for taking your time to help me out on this project.
Anthony

 

[Boncuk]

Hi Anthony,

here is a classic H-bridge using relays and limit switches.

The schematic is self explanatory if you follow the the paths according to UP/DOWN signals from the receiver.

The receiver should put out 0.7 to 1V (12V without problems. The base resistors are dimensioned for an input voltage of 12V)

The PCB is 1.95X2.25". Relays are designed for 4A current.

Regards

Boncuk

 

[KeepItSimpleStupid]

Right now, it's late and I'm tired and I have issues to deal with tomorrow. I took your diagram and put two circles on it. You would put your limit switches there, so that each would open that wire when they reached the respective limit.

Give me a little while for the remote interconnects.

 

[KeepItSimpleStupid]

Wow! Thanks for waiting patiently.

I put together a quick cartoon. The relays on your controller are labeled NO for Normally open, NC for Normally closed and C for Common. You have one for UP and one for down.

You know where to put the limit switches.

This diagram essentially connects to the switch in your diagram at Common of the switch, the UP position and the Down position.

You don't have to actually connect the manual switch, but you may want the manual switch to be (on)-Off-(on) where (on) is momentary on.

If you want momentary causes a position change, you will need the extra dual coil latching relay. I'm not sure you want to go that way. Let me know if you want a diagram for that?

 

[alec_t]

A modification of the arrangement in post #8 would be to use the momentary action switch to apply 12V via a resistor to the gate of an SCR (one per relay required) to switch on the appropriate relay coil. This would provide a latching action. A respective limit switch in each coil path would interrupt the SCR current to unlatch the circuit.

 

[nordic95]

Whats an SCR? What type oof coil and size resister would I need? Could I order these parts online or a local store here in the states?

Thanks Anthony

 

[KeepItSimpleStupid]

SCR theory: http://www.electronics-radio.com/articles/electronic_components/scr/what-is-a-thyristor.php

SCR's can be triggered by too high of a dv/dt so snubbers are required. This is an RC network from Anode to Cathode.

http://search.digikey.com/us/en/cat/discrete-semiconductor-products/scrs-single/1376387?k=scr

They also have a leakage current that needs to be considered, but the limit switch would alieveite that problem.


What I gave you earlier was smaller than this one: https://www.electro-tech-online.com/custompdfs/2012/01/RR2KPSeries.pdf

This would be easier to wire, but a lot more expensive. I'd guess about $30 + $10 for the socket.

http://www.galco.com/scripts/cgiip.exe/wa/wcat/itemdtl.r?listtype=&pnum=RR2KP-UC-DC12-IDEC

This contains a check button, which means you can activate the coils mechanically. The socket is extra.

 

[alec_t]

KISS has linked to an SCR (thyristor) explanation and mentioned the necessary snubber.

What type of coil and size resistor would I need?

The coil is part of the Bosch (or other) relay. An SCR (e.g. type C106D) typically needs about 0.2mA minimum to trigger it on, so a resistor in the range 10k-33k would suit. Once triggered 'on' an SCR stays 'on' until its anode/cathode current is interrupted (by the limit switch opening).
Any half-decent local electronics parts supplier should stock at least one type of SCR which would be ok.

 

[solaron]

re: circuit diagram for motor reverse control

If I substited a couple of time clocks to activated the circuits, would that create any problems?

 

[alec_t]

Activation by clocks is certainly doable, but the circuit complexity would depend on what sort of outputs the clocks have.

 

[4pyros]

You may have to readjust the timing all the time do to mechanical variables that you can not control on what ever you are moving.
IE. It may only take 1 minute to hit a limit in the summer but 2 minutes in the winter.