12 VDC Relays

if you want to power the motor ON, and OFF, and also be able to REVERSE it, you will need a different type of relay.   What you really need is to have the motor powered via an E unit, or better still, a Dallee electronic reverse unit, stepped through its 4 "positions" by sending pulses to it via the fob xmtr and recvr.

Depends on what you are controlling.  A typical reversing unit forces you into a Forward-Neutral-Reverse-Neutral sequence.  What happens if you want to move the mechanism Fwd, stop, move Fwd a bit more, stop, move Fwd yet again, stop, etc.? So if you don't mind being constrained to the F-N-R-N sequence then a Reversing Unit with a single-channel tx/rx pair as you show ought to work fine - with the relay interrupting power to the Reversing Unit similar to pressing the Direction Button on a train controller.

OTOH if you want one button that controls direction, and a 2nd button that activates the mechanism, then I can see going with the 2-channel tx/rx pair.  Though depending on the motor you might need to be mindful of switching direction while the motor is spinning since this can cause violent braking/reversal. 

Also, do you want a single direction button that toggles direction on each press vs. 2 buttons - one for Fwd, another for Rev?  Likewise do you want a go/stop button that toggles action on each press vs. 2 buttons - one for Go, another for Stop.   Or maybe you only want to Go when the button is pressed and Stop when released.  Perhaps you've already researched all this but different tx/rx remote relay modules offer different modes of operation referred to as "momentary" or "toggle" or "latching" and so on.  To each his own but I like the so-called "learning" modules which allow you to program/teach the module which mode to use.

If going with those low-cost remote relay modules on eBay be sure you can see the instructions before you buy.  Perhaps things have improved but when these first flooded the market the instructions were nothing less than cryptic.  Then various folks starting improving the English translations, discussing them in DIY chat-rooms, making youtube how-to videos, etc..

Easiest way to handle remotely controlled reversing is a latching DPDT relay. Also, you can prevent sudden direction changes at high speed with a "brake" relay which shuts down motor power whenever the direction relay is energized. Have published several articles detailing this approach.

BOB WALKER posted:

Easiest way to handle remotely controlled reversing is a latching DPDT relay. Also, you can prevent sudden direction changes at high speed with a "brake" relay which shuts down motor power whenever the direction relay is energized. Have published several articles detailing this approach.

That's kind of what I was thinking, Bob.  I'm trying to work out a wiring diagram for such a circuit.  The basic info is as follows;

12 VDC motor.  The motor would power a crane, let's say.  I want the crane to be able to swivel left and right.  There must be an off position so that the crane can be idle.  

The same basic set-up would also go for the hook.  The hook must travel up and down and also be idle between sequences.

Since those Key-fob transmitter/receiver set-ups operate on 12 VDC, the same battery can power the crane and also the DPDT relay or relays.  It would be interesting to see a wiring diagram.

In the past I have made operating cars for my garden railway using more elaborate or should I say cumbersome circuits.  I would like to simplify things using relays.  

Here is an example of the type of circuit I used on an LGB Matra crane.  Look at the area highlighted in yellow.  Disregard the AAA battery notes below.  Each operation required two channels on the receiver.  The highlighted diagram is repeated for the boom up/down and the hook.

https://youtu.be/jFNIfV8RZ7w

I couldn't get your video link to work so duplicated it below. 

The geared motors are moving slowly and can "safely" stop on a dime when power is removed.  I assume this is related to your recent thread about remote controlled relays: 

https://ogrforum.ogaugerr.com/t...21#57038617560657921

PLCProf had the answer on how to solve the 2-battery problem you marked yellow in your diagram.  Take advantage of the SPDT capability of your remote relays (presently you are only using them as SPST relays).  

Press remote button for RCVR1 and the Boom goes one direction.  Press remote button for RCVR2 and the Boom goes the other direction.  Press neither button and the Boom is idle.  The receiver relays should be set for momentary mode (a.k.a. jog/inching/non-latch) where the relay is closed only as long as the remote button is pressed.

You don't need an external DPDT relay and you only need 1 battery.  

Two channel wireless control dc relay. Useful for on/off and reversing of small dc motors. From China. Price $2.88 plus free shipping on EBAY.

pro hobby posted:

Two channel wireless control dc relay. Useful for on/off and reversing of small dc motors. From China. Price $2.88 plus free shipping on EBAY.

$2.88 (free shipping) is just for the 2-button remote fob.  That particular vendor charges $7.88 (free shipping) for what you have in your photo.  $7.88 is a nevertheless a reasonable price.