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Mick Bonwick

Decoders for mtb Point Motors

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I have recently bought a couple of mtb PM1 point motors to use as potential replacements for Cobalt-SS motors that are not suitable for my purposes. Thinking that I could use an existing DCC Concepts decoder (AD2fx) to drive them, I got everything ready this afternoon. Then I discovered that the PM1 needs three wires from a decoder and the DCC Concepts AD2fx decoder only produces two. I am hoping not to have to buy yet another decoder to try out these point motors, so am asking if anybody knows of a way to turn 3 x mtb wires into 2 x AD2fx wires.

 

This situation also raises the question, "How many more point motors are there that need 3 wires to drive them, other than solenoid types?" I might want to play with evaluate them at some point, too. :P

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Mick

 

The DR4018 works perfectly with the MTB MP1 motors. you can also purchase a converter that goes from 2 wire outputs to 3 wire and IIRC it is Digikeijs that make that also, but the DR4018 is a very easy way to control them.

 

I can honestly say you wont be disappointed with the motors, I have just purchased another 8 which gives me 24 :), I know that since I first mentioned them here many other people have bought them and I am not aware of any negative remarks.

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Iain,

 

Many thanks for the information. I will investigate the converter - I'm not keen on buying more decoders. If push comes to shove I'll use a couple of not-quite-working-properly Cobalts rather than buy more 'stuff.' The MP1s (not PM1s as previously stated - they're SEEP solenoids! :rolleyes:) were bought on recommendation, but I didn't ask the right questions before committing to them.

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Mick

 

I think that this is the units I am thinking off

 

https://www.dcctrainautomation.co.uk/digikeijs-dr4102-point-crossing-interface.html

 

i would give James a ring on Monday if you want to order and confirm that I have the right part. They also do a 4101 and a 4103 but I dont think they are the right bits - and as you bought the motors from him he will be very helpful :)

 

 

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It should just be a simple relay to switch the power around from two-wire reversing to three-wire. 

The one's Iain refers to should work if wired appropriately.   They're not as cheap as many relay modules(*) on Amazon/Ebay/etc..  but, if only two motors required, then paying extra may be worth it for a DCC dealer who'll support you.   

 

(* there are lots online, a four-relay module (so four motors) is between £5 and £8 from a variety of suppliers ).  

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27 minutes ago, Nigelcliffe said:

It should just be a simple relay to switch the power around from two-wire reversing to three-wire. 

The one's Iain refers to should work if wired appropriately.   They're not as cheap as many relay modules(*) on Amazon/Ebay/etc..  but, if only two motors required, then paying extra may be worth it for a DCC dealer who'll support you.   

 

(* there are lots online, a four-relay module (so four motors) is between £5 and £8 from a variety of suppliers ).  

 

Thanks, Nigel. While I understand what you say, I was completely bemused by the vast array of items that appeared in response to my search string of 'relay module'. I was expecting to see something with two terminals at one end and three at the other. While the idea of buying something you don't understand, and then playing with it to work out how it is used, is appealing, I think I'll follow your and Iain's advice in this instance and call a retailer for help.

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Posted (edited)
11 hours ago, Mick Bonwick said:

 

Thanks, Nigel. While I understand what you say, I was completely bemused by the vast array of items that appeared in response to my search string of 'relay module'. I was expecting to see something with two terminals at one end and three at the other. While the idea of buying something you don't understand, and then playing with it to work out how it is used, is appealing, I think I'll follow your and Iain's advice in this instance and call a retailer for help.

 

Further thinking....    I think this may work.   If you have two diodes around, its simple to try.  I don't have a MP1 motor, so can't confirm it.  But instructions imply it works with anything applied to the terminals.

 

688746316_Annotation2020-08-09105905.png.daddb897729cd507d7d0fb253da8f167.png

 

EDIT - scrub the above idea, Iain's comment below makes it clear the MP1 needs a particular polarity on the terminals, so it won't work. 

 

 

Edited by Nigelcliffe
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Nigel,

 

unfortunately the centre terminal needs to remain +ve with the switching terminals -ve :(

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Posted (edited)
8 hours ago, WIMorrison said:

Nigel,

 

unfortunately the centre terminal needs to remain +ve with the switching terminals -ve :(

 

Thanks Iain.   Unfortunately the manual for the MP1 wasn't totally clear on that detail !   

 

Something with a few transistors should be possible.   

 

Edit,  think this does what's required.   I'm fairly certain the blue diodes are unnecessary, and just a wire would suffice. 

 

1872834636_Annotation2020-08-09230039.png.77588afbf926ab85e04071a6ffde5132.png

 

Edited by Nigelcliffe
added another possible solution
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The MP1 uses a microswitch to switch contacts at the end of travel, killing power to the motor and making the second contact live and ready for the return move. It also requires 130mA to drive the point motor.

 

When I replaced 40 Peco solenoid point motors with MP1s last year the original MERG solenoid decoders wouldn't work and after much consultation we concluded that the best option was the DR4018. At a price of just over £4 per MP1 output, good value too. Any spare outputs can be programmed for a multitude of other things apparently.

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Thanks very much to all you respondents. I now know a bit more about point motors and decoders than I did two days ago.

 

I will not be replacing the Cobalt-SS motors with the MP1s, so will not need to obtain a DR4018. I have two Cobalt Classic point motors which have broken internal switches, so will use those and some microswitches to achieve the replacement. All I need to do now is to create something that will change the direction of travel of the Cobalt operating wire through ninety degrees and, because that is a mechanical operatrion rather than an electr(on)ic one, I have a fair chance of being successful.

 

I will keep the MP1s for a rainy day. My 38 SEEP PM1s continue to give me good mechanical service after being in place for several years, so I have no need to replace them, but that does not really have any bearing on the operation of two point motors bought for an experiment, albeit a failed one.

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5 minutes ago, Mick Bonwick said:

..........

 

I will keep the MP1s for a rainy day. ...............

 

See simple edit of my post above with another diode circuit.  That may do the job.  

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3 minutes ago, Nigelcliffe said:

 

See simple edit of my post above with another diode circuit.  That may do the job.  

 

Nothing to lose. That will be worth a try, so thanks, Nigel.

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