I've assigned myself a project to get a tortoise switch machine working with 2 green/red LEDs, to indicate direction on a control panel. Lots of reading about LEDs, Ohms law, resistors, forward voltage, breadboards, etc.
It looks like one typically uses 5MM diodes with a 20 milliamp current draw. I would be using 2-color LEDs for this scenario.
Assuming I use a power source of 12 volts and I want to hook up 10 turnouts this way (each with 2 LEDs). Is that enough voltage? How can I compute how many turnrouts a power source can support using this approach?
Thanks!
I will leave it to others to do the math, but here is my experience with powering multiple Tortoises.
On my old layout, I had over 60 Tortoises which were controlled by DPDT toggle switches on four control panels. Each control panel handled about 15 Tortoises, powered by an MRC Railpower 1370 power pack.
Each Tortoise (or pair of Tortoises on crossovers) was activated by a DPDT toggle switch and a single bi-polar (red/green) LED to indicate direction of the turnout(s). Each power pack was capable of controlling all 15 Tortoises and LEDs.
The LEDs required resistors, of course, but with single LEDs I never had to use diodes.
Rich
Alton Junction
ChrisVAAssuming I use a power source of 12 volts and I want to hook up 10 turnouts this way (each with 2 LEDs).
a Tortoise machine draw about the same amount of current as an LED (~10ma) which is why LEDs can be wired in series with the switch machines.
10 tortoise machines with series resistors would draw ~100ma
greg - Philadelphia & Reading / Reading
dup after 403 error
Yes, the Tortoise itself acts to limit current, just as a resistor would, so resistors are unnecessary.
I prefer to run my Tortoise machines around 8 or 9 volts. They move slower that way, and I think it's more realistic.
It takes an iron man to play with a toy iron horse.
richhotrain Each control panel handled about 15 Tortoises, powered by an MRC Railpower 1370 power pack.
I also use MRC Railpower packs hidden beneath the scenery. I can't say for sure how many can be powered, but I know from experience they can handle at least 40 with no problem.
MisterBeasleyI prefer to run my Tortoise machines around 8 or 9 volts. They move slower that way, and I think it's more realistic.
I also run my Tortoise switch machines at a lower voltage between 7 and 9 volts.
-Kevin
Living the dream.
If you feed the Tortoise 12V, and have an LED in series, you are runnign the Torotise on under 10V, so don't cut it down TOO far. You have to factor in the voltage drop of the LED. They do run a lot quieter at 8-9 volts with no real loss of holding power.
Most measurements I've seen put the Toroise at 15ma. TYhat means 10 of them would be 150ma. 40 of them is 600ma, well within the capability of a 1 amp power supply. 100 of them is 1.5 amps - I'd get a pauirt of 1 amp power supplies and run half on one and half on the other, if I had 100 Tortoises. Don;t run any power supply continuously at 100% of its rating. Say you calculate you will need 200ma to run your Tortoises. Don't get a 200ma power supply, get one 20-25% larger.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I'm certain that I used 5mm bi-color (red / green) LEDs from All Electronics, some years ago. Wired as Greg shows above. They offerred some nice LED panel holders. One of the two pieces of the holder fit snugly into the right size hole in my aluminum control panel and the LED just force fit into that.
I powered mine using a Circuitron 12v wallwart, which at the time I believe was a "regulated" type? Constant voltage at varied loads, I think?? Not sure about that but someone can comment on regulated, filtered, etc.
20200603_154226 by Paul Ahrens, on Flickr
I do suggest adding a fuse holder and fast blow fuse downstream of the power supply so a wiring error just requires a cheap fuse replacement. I do that for all my 12v supplies for lighting, etc.
Paul
Modeling HO with a transition era UP bent
Yes, a regulated power supply shoudl put out the specified voltage (withing a few tenths of a volt) across the range of no load to whatever the maximum ststed load is. And unregulated power supply may put out the stated voltage at say 50% load, at 10% load, it may be a volt or two higher, at full load, a volt or two lower.
FIltered means it has a filter capacitor to smooth the rectified DC - since AC is a varying sine wave, when you rectify it, you don;t get a nice flat line, you get little humps. The filter capacitor smooths out those humps. Tortoises like filtered power because those humps in the DC can make the motor hum.
Most any regulated power suppyl will be filtered, as voltage regualtors don't really like the non-smoothed DC either.
Two layouts ago, I uses the bi-color LEDs, but I used 2 of them on each Tortoise, wired opposite one another. I put them on my panel diagram in the diverging tracks. So the selected one lit up green, and the opposite one was red. Flip the ttoggle to change the points, and the green one changed to red, and the red one changed to green. I used a full 12V to power them, because I had 2 LEDs in series with the Tortoise motor - at about 2V each, the Tortoise motor got 8V from the 12V supply.
Our club some years ago used some of those machines with 12 vdc. We eventually used a 317 regulator for 9vdc to slow down the point movement and used a bipolar red green LED for direction.
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.