Emmo Posted June 26, 2018 Share Posted June 26, 2018 I use H&M point motors and rely on the frog polarity switches on them as well as the actual point blade contact. Both are not ideal and prone to fail and I was thinking of making up a bank of mini levers (aka Hornby style) to use as simple switches for the polarity, the metal lever being the common (frog). With me so far? Obviously one would have to switch the blades with the electrical switches I already have on my panel to operate the motors, but as a back up, you would also switch the Hornby style lever to ensure polarity has changed. Would this work do you think, or would it cause an electrical short if the blades/built-in H&M polarity switches made actual contact and you’d forget to switch the Hornby lever, which would still be left on the previous polarity? Link to post Share on other sites More sharing options...
DCB Posted June 27, 2018 Share Posted June 27, 2018 (edited) I use H&M point motors and rely on the frog polarity switches on them as well as the actual point blade contact. Both are not ideal and prone to fail and I was thinking of making up a bank of mini levers (aka Hornby style) to use as simple switches for the polarity, the metal lever being the common (frog). With me so far? Obviously one would have to switch the blades with the electrical switches I already have on my panel to operate the motors, but as a back up, you would also switch the Hornby style lever to ensure polarity has changed. Would this work do you think, or would it cause an electrical short if the blades/built-in H&M polarity switches made actual contact and you’d forget to switch the Hornby lever, which would still be left on the previous polarity? You are bound to set the polarity differently on the switch and the motorised point and short everything out. I use ridiculously cheap chinese micro switches from ebay on H&M point motors and on non motorised points as well for polarity switching, on DC. They can cope with around 1 amp, you would need something rather more robust for DCC.. Edited June 27, 2018 by DavidCBroad Link to post Share on other sites More sharing options...
Emmo Posted June 27, 2018 Author Share Posted June 27, 2018 You are bound to set the polarity differently on the switch and the motorised point and short everything out. I use ridiculously cheap chinese micro switches from ebay on H&M point motors and on non motorised points as well for polarity switching, on DC. They can cope with around 1 amp, you would need something rather more robust for DCC.. Can you send me a link please for these micro switches and any advice on wiring them up please. I am strictly DC. Cheers. Link to post Share on other sites More sharing options...
Pete the Elaner Posted June 27, 2018 Share Posted June 27, 2018 (edited) They can cope with around 1 amp, you would need something rather more robust for DCC.. Why? The switch is only to power the frog, on which you can only fit 1 loco. The current requirement for this between DC & DCC should not be any different. I agree that microswitches are the way to go. Simple, cheap & reliable. They just take a little care to set up properly. Edited June 27, 2018 by Pete the Elaner Link to post Share on other sites More sharing options...
cpman46 Posted June 27, 2018 Share Posted June 27, 2018 Why? The switch is only to power the frog, on which you can only fit 1 loco. The current requirement for this between DC & DCC should not be any different. I agree that microswitches are the way to go. Simple, cheap & reliable. They just take a little care to set up properly. Attached is a picture of an H&M point motor with a small microswitch added to switch the frog polarity as fitted to a friend's 00 layout. From left to right the microswitch connections are NC normally closed, NO normally open, C common. Mike Link to post Share on other sites More sharing options...
ejstubbs Posted June 27, 2018 Share Posted June 27, 2018 I prefer to use a miniature locking relay which is energised by the same pulse that fires the point motor. I think (though I couldn't actually produce concrete evidence) that solenoid activation of the frog polarity switch is more reliable than a mechanical linkage, which always strikes me as being a bit of a Heath Robinson approach. A relay is bit more expensive than a microswitch, though. Link to post Share on other sites More sharing options...
Emmo Posted June 27, 2018 Author Share Posted June 27, 2018 Attached is a picture of an H&M point motor with a small microswitch added to switch the frog polarity as fitted to a friend's 00 layout. DSCN0649.JPG From left to right the microswitch connections are NC normally closed, NO normally open, C common. Mike Where do I get these things from? Link to post Share on other sites More sharing options...
Crosland Posted June 27, 2018 Share Posted June 27, 2018 Why? The switch is only to power the frog, on which you can only fit 1 loco. The current requirement for this between DC & DCC should not be any different. Like ALL wiring in a DCC system, the microswitch must be able to withstand an indefinite overload close to the full booster current. It's a bit of a corner case, I know, but it has to be considered and should be allowed for. It must also be able to SWITCH that current, i.e. interrupt it in the event you change the points to clear the overload. If the 1 Amp rating is the DC rating then the switch may well be OK. AC ratings are always higher for switch contacts since any arc will be extinguished as the current passes through 0. Link to post Share on other sites More sharing options...
cpman46 Posted June 27, 2018 Share Posted June 27, 2018 Where do I get these things from? Try CPC http://cpc.farnell.com/multicomp/dm1-01p-30-3/microswitch-spdt-1a-short-lever/dp/SW05201 Mike Link to post Share on other sites More sharing options...
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