Ecm point motors

[Grahamrfd]

Hi, I'm looking for a wiring diagram for these old motors as I can't work out how to switch it. I have around 12 of them but not sure if they all work or not.

Thank you

[Nigelcliffe]

Guesswork from the photos: 

 

3 contacts, so that's likely "left, common, right".  (But it might be "left, right, common" or "common, left, right").    

Two diodes behind the connectors, and a conventional motor. I can also see some breaks in the tracks, and contacts on the sliding block, which indicates the movement of the block will disconnect power from one side or the other, so motor stops at end of travel. 

 

The diodes suggests a couple of possible approaches: 

a) diodes are to half-rectify AC for operation on AC (really common supply in its day).  

b)  Diodes limit travel in given direction using internal switch - the tracks inside suggest this may be the case, with the sliding block at the end connecting tracks in the top to the tracks in the bottom.    

 

So, I'd do the following:  

Use a 12v DC supply.   Put one side (-ve) on the centre contact, and try the +ve to each of the other contacts in turn and see what happens, if the motor auto-stops at one end, try the +ve on the other contact and see if it now runs back.   If nothing moves, swap the +ve and -ve over and try again. 

The same, but with a 16v AC supply. 

 

 

- Nigel

 

[Grahamrfd]

I've tried I tonight using a 9v battery and although it does move I have to alter the polarity to get it to reverse. I don't have access to an ac supply at the moment to try that but maybe that will work

[Brian]

As its an electric motor (not a solenoid) it will need the polarity reversing to make it move back to the original position. A 12V DC regulated power supply and a DPDT switch will do the job! 😀

[Nigelcliffe]

16 hours ago, Grahamrfd said:

I've tried I tonight using a 9v battery and although it does move I have to alter the polarity to get it to reverse. I don't have access to an ac supply at the moment to try that but maybe that will work

 

I assume your testing was -ve to common, and +ve to one of the terminals.   Then discovering the battery had to be reversed to reverse the motor.  

That does seem to suggest the "AC" idea was correct.   Which would also fit with the way people tended to wire their turnouts "back then". 

 

A DC supply could be used instead:    connect the two "switch" terminals together, and feed the combined pair and the "common" with DC.  Reverse the polarity with a DPDT switch.    Requires two wires from panel to turnout.   An AC version would require two wires plus a common return.  

 

 

[Grahamrfd]

19 minutes ago, Nigelcliffe said:

 

I assume your testing was -ve to common, and +ve to one of the terminals.   Then discovering the battery had to be reversed to reverse the motor.  

That does seem to suggest the "AC" idea was correct.   Which would also fit with the way people tended to wire their turnouts "back then". 

 

A DC supply could be used instead:    connect the two "switch" terminals together, and feed the combined pair and the "common" with DC.  Reverse the polarity with a DPDT switch.    Requires two wires from panel to turnout.   An AC version would require two wires plus a common return.  

 

 

Thanks for your advice, I'll hopefully get home early enough tonight to try it with 16v ac, assuming I can find my old hm controller. Failing that I'll go down the route of using dpdt switches with 12v dc

[Grahamrfd]

All sorted, runs off 16v ac, left hand terminal is common, other 2 for left and right throw

[Brian]

Of interest.. Does DC do the same? i.e. Left hand terminal to negative while applying a positive to one of the other two causes the motor to move over and then applying a positive to the other makes the motor move back again?

Edited September 27, 2023 by Brian

[Grahamrfd]

12 hours ago, Brian said:

Of interest.. Does DC do the same? i.e. Left hand terminal to negative while applying a positive to one of the other two causes the motor to move over and then applying a positive to the other makes the motor move back again?

No, you have to put positive of the left hand terminal and negative  to the other to return the movement on dc. It's doable with switching but I want to use the switches for changing leds on the panel so if I can keep the points to one pole of the switch then all the better. Now to find my old 16v ac transformer

[Nigelcliffe]

There's an alternative DC powering method,  the "split" or "stacked" power supply.   I'm fairly certain this works on these motors (which I've only seen the photos) because of the two diodes on the motor.   

 

Two DC supplies, of around 9v to 12v DC(*).   Arranged so the -ve of one supply is connected to the +ve of the other.   This gives three output wires which one can think of it as -9v, 0v, +9v,   or -12v, 0v, +12v.      (where zero lies is an arbitrary decision of the person measuring).  

 

The 0v goes to the common on all the motors.   The -9 and +9 are switched by a SPDT switch, and the single wire from the switch goes to both of the switching terminals.    When the motor sees -9v it rotates one way, when it sees +9v it rotates the other.  

 

This gives:  DC power sources, only one wire from panel to motor (plus common return for all motors) and uses SPDT switch.   The same switch can illuminate LEDs on a panel.  

 

 

(*)  Critically these supplies must not have the 0v connected to "mains earth".   So, two-pin DC power bricks only (ie, no earth wire, or a plastic earth pin).   Some three-pin DC power bricks connect the 0v to the mains earth pin, and a simple rule of two-pin only means one avoids the risk.  

 

 

 

Alternatively, with Brian's preference for standard DC and a DPDT switch;  that would also work, but requires two wires from panel to motor (and connecting the two "switched" terminals together with one of the DC wires).   Panel indicators could run from the DC output of the switch by wiring the LEDs (and series resistor) over the output - switch one way and a LED lights, the other way and LED doesn't light.   Orient the LED so it lights appropriately. 

 

 

 

- Nigel