RMweb Gold Fen End Pit Posted October 14, 2009 RMweb Gold Share Posted October 14, 2009 I hadn't come across these before having used Fulgarex and Lemaco on Fen End Pit and tortoises on the P4 layout. However I had bought a Hoffman Mk1 from Finney and Smith last year and used it to drive a ground signal. I tried to get some more from them at Scaleforum but balked a bit at the ??13.95 price tag for the Hoffman Mk 2. Still I bought one and tried to wire it up in the same way I had used the Mk 1. On the Mk 1 there are two brown wires with attached diodes and a red wire as a return. The idea is that you wire them up so that you can send the 'top half' of an AC for one direction and the 'bottom half' for the other. This works great and my level frame is wired so each micro-switch switches the output between the positive and negative half of the waveform. This works for my tortoises, Hoffman Mk1 and LED colour light signals. HOWEVER, the Hoffman Mk 2 is now wired completely differently as it incorporates some kind of speed controller and I couldn't work out how to use it with the wiring from the existing switch on the frame. Doing a bit of digging on the interweb I found references to the 'conrad' point motor which looked to all intents and purposes identical to the Hoffman Mk1. These are available from Conrad Electronics From their website there appeared to be two types. 219998-8a Point mechanism with switch and polarity reversal 219999-8a Point mechanism with limit switch and polarity reversal I couldn't see any difference between the descriptions on the site at all. The 219999-8a appears to be ??6.95, not bad I thought, half the price of the Hoffman MK2 from Finney and Smith. The 219998-8a had been reduced to ??3.95! I've just taken delivery of 5 and I can't say I can see ANY difference between them and the Hoffman MK1. Given I don't need ultra-slow speed for the ground signals this seems like a bargain. one word of warning Conrad-uk use the Home Delivery network to ship their goods and so when I was out the parcel was taken away to some distance depot. It finally made it on the second attempt. Makes you appreciate your friendly postie who knows he can just stick it in the garage! David Link to post Share on other sites More sharing options...
77philg Posted October 14, 2009 Share Posted October 14, 2009 Do these work as the hoffman mk2 on a straight on/off /on switch , not a passing contact switch? phil Link to post Share on other sites More sharing options...
RMweb Gold Fen End Pit Posted October 15, 2009 Author RMweb Gold Share Posted October 15, 2009 Do these work as the hoffman mk2 on a straight on/off /on switch , not a passing contact switch? phil Yes, if you are using an AC voltage, see diagram David Link to post Share on other sites More sharing options...
dave_long Posted November 9, 2009 Share Posted November 9, 2009 Hi I have these on a small layout and they work quite well in fact. However the version 219999 does not have the polarity switch that the version 8 has. They are exactly the same as the Hoffman mk1 was, as Hoffman and Conrad worked together to produce these little motors, however they went there seperate ways, the reason the Hoffman mk2 is more expensive is due to it having a decent microswitch inside it, instead of the mk1/conrad version which relies on copper brushes which are not as fail proof as a microswitches but much cheaper to produce. Being AC they won't however work off a DCC wave current, but the need of an AC current from a transfomer is required. Although they are not strictly slow motion point motors you can reduce their throw speed by reducing the AC current slightly. hth Link to post Share on other sites More sharing options...
meple Posted November 9, 2009 Share Posted November 9, 2009 They're not AC they are DC that's why you need the diodes. Link to post Share on other sites More sharing options...
dave_long Posted November 9, 2009 Share Posted November 9, 2009 They're not AC they are DC that's why you need the diodes. The operating voltage is 16VAC.? Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted November 9, 2009 RMweb Gold Share Posted November 9, 2009 The Conrad motors will work from half wave rectified DCC (i.e. using a DCC supply with a diode in series) but I found they worked better on a lower voltage, I ran them from 9 volts instead of 12, it made them a little quieter. I had lots of problems with them due to the design of the switching so eventually upgraded to tortoise instead. I've still got two dozen of them sat in a cupboard here somewhere. Andi Link to post Share on other sites More sharing options...
RMweb Gold Fen End Pit Posted November 9, 2009 Author RMweb Gold Share Posted November 9, 2009 The Conrad motors will work from half wave rectified DCC (i.e. using a DCC supply with a diode in series) but I found they worked better on a lower voltage, I ran them from 9 volts instead of 12, it made them a little quieter. I had lots of problems with them due to the design of the switching so eventually upgraded to tortoise instead. I've still got two dozen of them sat in a cupboard here somewhere. Andi I have standardized on tortoises for the point operation, but I wanted something to operate ground disk. These take hardly any omph to move, the speed isn't as much of an issue and I don't require any polarity switching for a frog. David Link to post Share on other sites More sharing options...
meple Posted November 9, 2009 Share Posted November 9, 2009 The operating voltage is 16VAC. Not after you have passed it through a couple of diodes it isn't. Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted November 9, 2009 RMweb Gold Share Posted November 9, 2009 I have standardized on tortoises for the point operation, but I wanted something to operate ground disk. These take hardly any omph to move, the speed isn't as much of an issue and I don't require any polarity switching for a frog. David This is one of the reasons I've kept the ones I've got, I may end up using them to run shunt signals on Ravens. Andi Link to post Share on other sites More sharing options...
dave_long Posted November 10, 2009 Share Posted November 10, 2009 Not after you have passed it through a couple of diodes it isn't. I get your point but It should be stated they need to be run from from an AC transformer. They are advertised as AC, so I really don't see the need for keep saying no they're DC? Link to post Share on other sites More sharing options...
RMweb Gold Dagworth Posted November 10, 2009 RMweb Gold Share Posted November 10, 2009 I get your point but It should be stated they need to be run from from an AC transformer. They are advertised as AC, so I really don't see the need for keep saying no they're DC? I think you may be misunderstanding how they work. They are DC units, if you connect them up to DC one way they will run to the end of their travel and stop. Reverse the polarity and they will run to the other end and stop, just like a tortoise motor. Because AC reverses its polarity 100 times a second, by using diodes to only take half the waveform you can save wiring, using two diodes and a switch as shown in the diagram allows you to select which half of the waveform (and therefore which polarity of half wave DC) reaches the motor. If you connected them directly to an AC supply without the steering diodes and switch the motor would buzz and let out a large cloud of foul smelling smoke. You can also run them off of split rail DC power supplies, where you would have +12volt, 0 volt and -12 volt rails. One side of the motor would be connected to 0volts, the other side goes to a switch that can select either +12 or -12 to determine which way the motor runs. Likewise you can also run them off a normal DC supply with a DPDT switch wired up as a reversing switch as you would find in most DC controllers. Tortoises can also be run from AC as per the diagrams in this thread but they are also DC units. For that matter so can any loco (don't try it if you have a DCC decoder fitted though) Andi Link to post Share on other sites More sharing options...
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