Alternative frog "juicer"

[Scottl]

I was searching around and came upon these little devices that seem to be functionally equivalent to the Tam Valley frog juicer.

http://www.gaugemaster.com/news/NEW-DCC-Autofrog-from-Gaugemaster

The circuit is clearly very simple compared to the frog juicer and the image and circuit board was enough to make me wonder how it worked.  A quick search found someone with a reverse engineered circuit attempt that is reported to operate.

http://www.ngaugeforum.co.uk/SMFN/index.php?topic=33870.0

This is rather interesting and may be a cost-effective alternative to a juicer.

[peteski]

Seems quite clever, but I personally try not to depend on mechanical relays whenever possible. Solid-state baby!    That circuit though is not really any better than using switch machine contacts to power the frog.

[Scottl]

I agree, solid state when possible.  I wonder if a SS relay could be substituted?  These circuits are handy when you don't have a switch machine.

[peteski]

I agree, solid state when possible.  I wonder if a SS relay could be substituted?  These circuits are handy when you don't have a switch machine.

If there is a solid-state latching relay, then I suppose it can be substituted. "Latching" in the key.  The way that this mechanical relay works is just like an Atlas twin-coil switch machine.  The relay has 2 coils. Energizing one coil throws the relay one way, energizing the other coil will throw the relay contacts in the opposite direction.  In the diagram the points are connected to the frog (the gap is only at the rails exiting the frog). The relay will throw when the points are thrown.  That is how I see it.

[C855B]

I did some quick looking around for such a relay, and while SSRs are getting really cheap, I found nothing resembling a latching style. Of course, you could use two SSRs fronted by a latching flip-flop, but at that point you need to build a local power supply for the flip-flop and add optoisolation for the inputs. IOW, by the time you've designed, purchased the various bits and built the thing, you've bought a Frog Juicer.

The Gaugemaster twin-coil relay is a slick trick. It probably works well when you hit the frog with a powered truck (loco or lighted car) that solidly bridges the gap to power the corresponding coil. However, what happens when a single metal wheel hits it at speed? Will there be enough time to move the contacts?

[Scottl]

I couldn't find one either.  I really don't know what the performance of the circuit would be but the reports on the forum were positive. 

Based on the reversed-engineered circuit, the parts are common and cheap so I would expect you could build one for a few dollars.