Back in Sept I started a thread asking for some help with a DipTrace project I was working on, linked here. It was a simple flip-flop multivibrator circuit intended to flash road crossing crossbuck leds. During development one idea suggested was adding a 2 gang pot to be able to vary the flashing speed.

The idea was dropped because no one knew of a source for small stacked trim pots. (You need a separate pot for each side of the circuit)

I just got a thing from ebay, one of those “items picked especially for you” deals. It turned out to be a 4 light road crossing signal with an actuator board, made by Eve. Price about 12 bucks. Check out the board:

Evoloution-Eve Flasher Jan 2020

Notice the nice adjustable trim pot, presumably two stacked. The rest of the circuit is exactly the same; 2 x 33uf caps, 2 x 200 ohm resistors, 2 x 50K resistors, and two npn transistors. Wonder where they got the pot idea?

 Coincidence, or are more people reading the OGR forum than we know? 

Rod

We are never too old to learn something stupid....

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Rod: Since this design was widely published from Forrest Mims, it only seems likely that someone else might get the same idea; not to mention that OGR does get it's fair share of listings from Google and other search engines.

Have you tried this module out at all? What do you think about their solution?

Leo; I only just found the above board listing, have not ordered one to try out. But the price seems reasonable for a board and a 4 light crossing head, all for $12. Hard to beat.

While developing the original fixed-speed circuit back in Sept, I also did a variation using a small top adjust single gang trim pot to vary the flashing speed. Then I did a 555 timer version that also has variable flash speed. I ordered boards for each and they both work well. Didn't publish them here because it didn't seem  like there was a whole lot of interest in being able to vary the speed. But if there is I can add them to the shared build files thread that rtr12 has running.

Rod

We are never too old to learn something stupid....

What's curious is that seller also has N and HO versions but those do NOT have that adjustable trim pot.  Go figure! 

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While it's not very sporting of me to Monday-morning quarterback, but for the same parts cost I would have added support for AC Accessory voltage input before adding the trim pot.

 

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