stevecamden Posted July 21, 2012 Share Posted July 21, 2012 I want to use the pulse on the R8247 decoder to initiate a ( essentially push/on/off) switch SPNO Do you think its OK to wire the two +12v outputs together so you have the common ( middle wire) and one wire from the decoder to activate a relay. So you get pulse on/off? Link to comment Share on other sites More sharing options...
Fishmanoz Posted July 21, 2012 Share Posted July 21, 2012 Hi Steve, what are you actually trying to operate. I ask because the decoder may be able to do it directly by adjusting its pulse length via its CVs. Link to comment Share on other sites More sharing options...
stevecamden Posted July 21, 2012 Author Share Posted July 21, 2012 I have inherited one of these new Dapol signals ( can I say Dapol on here) anyway - it has 2 wires that are just a push on/off circuit make to operate it. The other 'power' for the signal cmes from a 16vAC ( goodness knows why) source. It has a in-built solenoid and looks quite nice, but I want to operate it from Railmaster using the R8249. Confused? Well so am I .... Link to comment Share on other sites More sharing options...
Rog RJ Posted July 21, 2012 Share Posted July 21, 2012 stevecamden said: I want to use the pulse on the R8247 decoder to initiate a ( essentially push/on/off) switch SPNO Do you think its OK to wire the two +12v outputs together so you have the common ( middle wire) and one wire from the decoder to activate a relay. So you get pulse on/off? Your idea would probably work OK but to be safe, I would fit diodes into the two feeds from the decoder to prevent feedback into from the "active" output back into the "inactive" output Link to comment Share on other sites More sharing options...
stevecamden Posted July 21, 2012 Author Share Posted July 21, 2012 Actually that was precisely my concern ( if only I could have put it more eloquently) Do you think just a standard diode on each pin (both) from the R8247 ( not the common) with the cathode leading from the decoder would be oK? Steve Link to comment Share on other sites More sharing options...
Gregd99 Posted July 22, 2012 Share Posted July 22, 2012 Steve, the main things to think about with the diode are the revers breakdown voltage and the forward current. do be aware that the two decoder outputs are open collector. this means that they look like "switches" to the outside world. I always forget if they are pull-down to gnd or up to 12V... Depending on circuit inside the signal it might be possible to connect them directly to the switch port on the signal. if you use a relay then check the coil current (I = V/R) required and this will tell you what you need for the diodes. I think you will also need to allow for the back emf voltage from teh relay coil as your diode will be in series with the internal decoder back emf protect. Link to comment Share on other sites More sharing options...
stevecamden Posted July 23, 2012 Author Share Posted July 23, 2012 Greg I keep forgetting too! Its always a bit 'worrying' when you have two black boxes ( both quite expensive). I am all for 'experimenting' but not at the price of a decoder or a signal solenoid. Relays are two a penny ( literally). I think there is a need for a device that can be operated from Railmaster or the Elite that just gives a momentary close ( push switch) No power. Steve Link to comment Share on other sites More sharing options...
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