Reversing Switch/Relay for 24V Electric

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NCBQGUY
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Reversing Switch/Relay for 24V Electric

Post by NCBQGUY » Wed Nov 22, 2017 6:21 pm

I bought a 24V Centercab 0-4-0 critter that has a nicely done beefed up homemade version of a Mr. Motion drive based on a Schwinn bicycle motor and controller.
Because bikes don't have much need for a reverse the builder provided a simple DPDT bat handled switch for reversing....mounted on the underside of the frame which would be a little inconvenient for switching.
Does anyone have any suggestions for a different setup that would be compatible with control with R/C components? I would like to avoid R.Goldberg setups if possible as I don't want bits that can go out of alignment in service.

Charlie Vlk

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DianneB
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Re: Reversing Switch/Relay for 24V Electric

Post by DianneB » Thu Nov 23, 2017 7:16 am

On my 7.5" gauge streetcar I used a 1KW electric scooter controller which didn't have reverse so I added a couple of 12 volt automotive relays (with the coils wired in series) controlled by a small toggle switch. (Relay: http://www.ebay.ca/itm/like/13185437049 ... dispItem=1) The inexpensive and reliable relays reverse the polarity to the motors. Works like a charm.

If the coil current is too high for your R/C equipment, you could add a small relay to switch the power relays.

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FLSTEAM
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Re: Reversing Switch/Relay for 24V Electric

Post by FLSTEAM » Thu Nov 23, 2017 7:25 am

As Dianne said you could also just use a single spdt 24v relay and an R/C relay. The power relay would be wired to forward as default.

John B.
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Atkinson_Railroad
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Re: Reversing Switch/Relay for 24V Electric

Post by Atkinson_Railroad » Thu Nov 23, 2017 8:41 am

Google "H Bridge Relay Circuit".

You'll find plenty of ideas, including connection diagrams.

URL Reference: https://www.google.com/search?lr=&as_qd ... ibgPS-DRHA

John

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DianneB
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Re: Reversing Switch/Relay for 24V Electric

Post by DianneB » Thu Nov 23, 2017 12:27 pm

FLSTEAM wrote:As Dianne said you could also just use a single spdt 24v relay and an R/C relay. The power relay would be wired to forward as default.

John B.
\

Afraid not. You need a minimum of TWO poles 'cause you need to reverse the connections between the motor and the controller.

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FLSTEAM
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Re: Reversing Switch/Relay for 24V Electric

Post by FLSTEAM » Thu Nov 23, 2017 1:54 pm

Sorry about that, you are correct...should have read DPDT 24V relay.
I didn't have my brain engaged before typing.

John B.
http://www.ngshay.com/
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NCBQGUY
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Re: Reversing Switch/Relay for 24V Electric

Post by NCBQGUY » Thu Nov 23, 2017 2:08 pm

Thanks for the replies.
Turns out this was covered in a current thread where a Dimension Engineering Syren50 controller was recommend.
On the linked diagram there are components pictured and in the wiring diagram that are not identified. It would be helpful to know what everything is and what the specs are for each part and what voltages are in each part of the wiring.
Anyone have experience with this unit? It looks like it may be just what I am looking for....
Charlie Vlk

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Fender
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Re: Reversing Switch/Relay for 24V Electric

Post by Fender » Fri Nov 24, 2017 6:38 am

Charlie,
A DPDT contactor (with the non-energized position for forward) is exactly what I use on my Davenport electric loco. One cautionary note though: don't reverse the engine while under power, because the contacts will arc and then reverse won't work anymore. Ask me how I know this.... :x
Dan Watson

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SteveM
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Re: Reversing Switch/Relay for 24V Electric

Post by SteveM » Sun Nov 26, 2017 9:33 am

Just be sure you use stuff rated for DC.

You might see switches / relay contacts rated for adequate amps at 110 or 220 VAC, but AC is not the same as DC. Because AC is constantly switching polarity, when the contact breaks, it stops arcing. DC doesn't do that.

Steve

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Re: Reversing Switch/Relay for 24V Electric

Post by skid-roe » Sun Nov 26, 2017 10:19 am

https://www.ebay.com/itm/10-30V-100A-30 ... 2749.l2649

Check out eBay,
I purchased a 24 volt 100 amp reversing PWM motor controller for $55

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SteveM
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Re: Reversing Switch/Relay for 24V Electric

Post by SteveM » Sun Nov 26, 2017 5:43 pm

skid-roe wrote:https://www.ebay.com/itm/10-30V-100A-30 ... 2749.l2649

Check out eBay,
I purchased a 24 volt 100 amp reversing PWM motor controller for $55
Interesting. Does it have dynamic braking?

Also, do you know if there is a user manual online?

Steve

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steamin10
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Re: Reversing Switch/Relay for 24V Electric

Post by steamin10 » Tue Nov 28, 2017 5:57 pm

Note to Steve M.
In my experience working on relay circuits, one way to shut down arcing from coil field collapse is to increase the air gap on the contacts. This is easily accomplished by using multiple contacts on the switch block, wired in series, so that opening multiplies the speed of the gap appearing in the circuit. This is general information but can be cheaply effective with surplus relays of various types. In battery powered circuits, remember not to build in holding designs that waste power. Rather build in default positions (Run, Forward) as default to return at shutdown.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
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