I have a Lionel CW80 which gives about 18 VAC in the accessory power output terminals. So I was thinking of using a single Diode for the + Wire, Put it into a DC-DC module convter (LM2596 I believe) With the LED, set output to 12 volts.
You do realize you can vary the accessory power setting of the CW-80 to any voltage you like, right?
@stan2004 I also need help, How Do i know which is the Positive end and negative end on the IR led and Colored LEDS in the diagram? Also for the IR reciever. Kind of confused on how to figure out where the polarity is
For the LEDs - including the infrared ones - it's pretty safe to assume the flat side is the "-" side (a.k.a cathode) and the rounded side is the "+" side (a.k.a. anode). Unfortunately, for the photo-transistor I've seen it both ways. What photo-transistor did you get?
For the LEDs - including the infrared ones - it's pretty safe to assume the flat side is the "-" side (a.k.a cathode) and the rounded side is the "+" side (a.k.a. anode). Unfortunately, for the photo-transistor I've seen it both ways. What photo-transistor did you get?
hmm well I meant connecting them to the diagram. How would I know which part is positive or negative? Ive got the same one you showed me on ebay
Give me the link to what you bought for the phototransistor.
For the LED, the following should help:
But to make a guess for the phototransistor, go with the "+" side as the longer lead and the "-" side as the short lead. The "+" side would be the collector and the "-" side would be the emitter - refer to the 2N3904 symbol.
Give me the link to what you bought for the phototransistor.
For the LED, the following should help:
But to make a guess for the phototransistor, go with the "+" side as the longer lead and the "-" side as the short lead. The "+" side would be the collector and the "-" side would be the emitter - refer to the 2N3904 symbol.
Perfect! and this one right here http://www.ebay.com/itm/200981...e=STRK%3AMEBIDX%3AIT
Do you have a DMM and if so what brand/model number?
Do you have a DMM and if so what brand/model number?
whats a DMM?
Digital Multi-Meter. I'd say essential for assembling circuits of this type.
Digital Multi-Meter. I'd say essential for assembling circuits of this type.
I acutally do Its a klein tools one, It was expensive around $90, I dont know the exact model name
Put DMM into Resistance or Ohms mode. Attach red and black meter leads across photo-transistor. In one orientation, the reading will be very high and will change little if aimed at a lamp, out the window, etc.. In other orientation the reading will be much lower...and will go lower if you aim the device at a lamp or other light source. When you find the latter case, then the red meter lead is connected to the "+" side (collector) and the black meter lead is connected to the "-" side (emitter).
Then report back whether the flat-side of the case is "+" or "-".
Or you can email the eBay seller and ask them which is which. Sometimes they'll even send you a datasheet which makes you wonder why they didn't include it in the listing in the first place...
Put DMM into Resistance or Ohms mode. Attach red and black meter leads across photo-transistor. In one orientation, the reading will be very high and will change little if aimed at a lamp, out the window, etc.. In other orientation the reading will be much lower...and will go lower if you aim the device at a lamp or other light source. When you find the latter case, then the red meter lead is connected to the "+" side (collector) and the black meter lead is connected to the "-" side (emitter).
Then report back whether the flat-side of the case is "+" or "-".
Or you can email the eBay seller and ask them which is which. Sometimes they'll even send you a datasheet which makes you wonder why they didn't include it in the listing in the first place...
Well the receiver/phototransistor has one long leg. Ill assume thats the anode? and What about the symbol for the phototransistor? Still dont know where + and - is on the diagram for it
Two pins on typical NPN IR phototransistor referred to as Collector (+) and Emitter (-). DMM method described earlier will tell you which is which on a loose part.
Or email the seller and ask.
If you have the rest of circuit already wired up, you can just hook up the phototransistor and see which orientation "works". For example, measure the DC voltage using the DMM at point indicated. If phototransistor is installed correctly, the voltage will be near 12V when dark and drop to a few Volts or so when light. If installed backward, the voltage will be near 12V whether dark or light.
Stan and John
I have followed thread on and for some time, so I might have missed something.
Can the Stan's common anode circuit schematic posted above drive a seven led position signal?
Hope this doesn't high jack this topic.
Gerry G
I assume you're talking about a PRR-type signal head. Is it a roll-your-own with "just" 7 LEDs wired in a common-anode configuration? If so, then in round numbers (there are some i's to dot and t's to cross) the circuit applies with the vertical LEDs powered by the "green" circuit, the diagonal LEDs powered by the "yellow" circuit, and horizontal by "red"...and the common center LED always powered since it is always on.
But if you have a off-the-shelf PRR-type signal it likely has the timing components built-in and you don't need the timing circuit (the 555 timing IC chip) to perform the timing. In other words, the circuit shown earlier is appropriate for a bare-bones signal head with "just" LEDs and wires as is the case with the eBay "wehonest" red-yellow-green head.
So as with most thing in life, it depends on what you have and what you want to do! If you are looking at rolling-your-own IR detector to replace a $25 ITAD (or whatever they cost these days) with $1-2 of IR optical components to trigger the signal head, that's another issue.
Stan
I'm looking to drive a "bare bones" PRR type positional light signal like the 3 LED "wehonest"signal with no delay mode. Therefore, from your answer above you are confirming that the circuit will in fact apply to each 3 LED position mode connected per your "wehonest" circuit. Additionally the center LED would remain on when the cathode is connected to -12v. I'm also assuming the R3 resistor value would be the same.
Thanx for your continued help.
Gerry G
I think I found the schematic (it's been several years!). Anyway, I modified it for a PRR style bare-bones 7-LED head. The circuit is the same. Now, rather than 1 LED being on at any given time you have 3 LEDs on. The center LED (LED7) is always on. The resistor R3 sets the LED brightness and you can use one of those online LED Resistor Calculator programs to tell you what resistor value to use to get some desired level of current for 3 LEDs of whichever type you are using. In practice just fiddle with different values of R3 until you find a brightness you like - it's kind of obvious when you overdrive an LED as it just seems too bright. Something between 1K (as shown) and 330 ought to be suitable...with brightness increasing as you decrease R3.
Stan
Thanx for the conformation and the updated schematic with brightness adjustment explanation. This helps a lot. The scary part is I think I'm starting to understand this stuff.
Once again thank you for all your help.
Gerry G
Are your signals common anode or common cathode? It will make a difference.
John
They will be common anode "roll your own" position signals as Stan calls them and connected per the updated schematic posted above.
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