Has anyone installed this circuit into a DC engine? I am hesitant to use it because I built the circuit and while testing it the bridge rectifiers get very hot and either it is supposed to get very hot (which seems wrong) or I’ve got something wired wrong…but I don’t think so. It really sucks the power up as well. Anyway, just wondering if anyone had any experience with it? I intend to light some old Athearn BB U30C’s (PRR)…headlights, number boards, back up lights…the other option will be to just make a simple LED circuit using a few LEDs and fiber optic filament. That is just LEDs + resistors. Very simple and no heat generated.
Just curious if anyone ever used this circuit. And wondering why? I found it through one of the forums … Not sure if it was MRR. Originally I was trying to see if there is anyway to light in DC and get so called lights on while the engine is standing still. Don’t want to use batteries. And it’s just not worth it to install DCC in these engines.
I am also using DC and I would not use this circuit. Being in series with the motor is going to cause a substantial starting voltage increase. It sounds like you already found that out.
When I do a re motor, flash removal, N/S wheels, more weight, etc, one of the goals is lower starting voltage @ a given speed, not a higher one.
That is what I do. If it already has low quality LEDs on a decent board like a Kato, I desolder and install better LEDs.
No light boards…these are your standard Athearn Blue Box models. The motors happen to be really clean and they’re strong runners. The heat coming off the bridge rectifiers was way to hot after hooking up the circuit to the motor with aligator clips. I just can’t figure out why anyone would use that circuit.
I’ll just go with the simple LEDs & resistors. They draw some current…using 1.8mm LEDs…I believe they need about 3 Volts but its a trade off…so you loose some power but its negligible I think?. And I’m planning on putting 2 lights up front and 2 in the rear. Have to see if that depleats the power to much.
Well, I have used 1/2 that circuit, but with a light bulb not an LED. That is I have one bridge rectifier with a 1.5V lamp across it. It works great.
In the circuit shown I don’t understand why there is the second diode in line with the LED. I assume it is limiting the reverse voltage to the LED. Even so why add the 2nd bridge rectifier forcing more voltage through the LED section of the circuit. I would replace the 2nd bridge rectifier with two diodes, in parallel of opposite polarities.
Are you using circuit components rated for high enough voltage and current?
And of course a locomotive equipped with such a circuit is going to have a higher starting voltage. That is the whole point. That pre-starting voltage is what lights the lamp.
In my DC jobs I do not have a double rectifier (as I know of), in this scenario, (the circuit above) it seems the goals were to really cut down the voltage to the LED’s, if each Diode eats 0.7 Volts, it would take that circuit 4.2 volts to begin to operate (my estimate), so yes, that is a dead initial start! Especially when you consider it is in series with the motor, add in that start voltage & you may very well be up high in the ‘Normal’ cruising range in a straight motored model!!!
I have not done an Ath BB lighting project in a while, but I have a few I’d like to!
Do not expect anything soon, but I will post here & give specifics, when I get to it.
The requirements I have will be;
1 Headlight
2 FWD Ditchlights
1 Rear Light
2 Optional Rear Ditchights (Branchline Road Switcher, -no turn table access).
1 Optional blinking Beacon
All in DC & directional, & directly wired, (no circuitboard cheats [like in a Kato])…
Here is what I meant about ‘using’ a Kato’s existing board.
I only needed to use a balancing resistor to make the the lamps on the cab & the ditchlights match in intensity, fairly easy.
Hope you find it interesting.
I used the exact components per the diagram. Radio Shack…LEDs from another supplier…I assume the components are rated high enough assuming the guy that posted the link knew what’s what?!?..
There are various circuits: using bulbs and LEDs, 1 bridge, 1 Led, directional and so on. I don’t know enough about electronics to answer why 2 bridge rectifiers or diodes in the particular circuit, only enough to get into trouble. I chose it because it was so called “constant, bi-directional” …obvious it ain’t gonna be constant in DC. I had come across a circuit that claimed to build up enough juice to keep the leds glowing after running for a minute or two…when loco stopped…in DC…still searching for the circuit…I’ll post it if I find it. But I’m just not clear why bridge rectifiers, diodes, etc.
So far can’t find a reason to use anything more complicated then leds + resistors (Or a circuit that’s gonna give you constant lighting in DC) Front and back. Reverse polarity turns them on and off…if wired accordingly. I’d like to have the whole array, marker lights, ditch lights, but will wire up headlights, number boards, reverse headlights for now…unless someone has a better alternative? These Athearns are sort of experimental for me. If I fry one I won’t like it but I’ve had them for 23 years sitting in the boxes … So not a huge investment…
and yeah, there is definite power loss to loco with all these LEDs wired in there. It’s a trade off.
Here is what I meant about ‘using’ a Kato’s existing board.
I only needed to use a balancing resistor to make the the lamps on the cab & the ditchlights match in intensity, fairly easy.
Hope you find it interesting.
And Chad…yep, limit the juice to the LEDs/bulbs sounds right…but when I hooked it up the LEDs were very bright…so I don’t know, but the result was the LEDs were on fire … Very intense. They were sucking all the voltage. The loco was struggling to move. I had the throttle ( a standard MRC transformer) at more then 1/2 way.
nice lighting on your GP35. I had come across an Athearn Dummy Lite Board…I believe they were coming with Athearn RTR units…seems they were being replaced/upgraded and the boards were plentiful…maybe 10 years ago…would love to find one…cheap…but no luck so far…I found one on eBay but I guess they’re scarce now so 15-20 bucks is not worth it for me…at this point…
maybe someone reading this have 5 of these boards laying around…(:…
Paul,
I really want to caution you, if you did what I did, the only drag would be ‘letting the smoke out’ of those LED’s, they would not stop your motor if wired properly.
One thing that would stop your motor is if they interrupted your power pickups, or the motor leads.
An LED, (or any diode) can only steal a 0.7 volt, if placed in the correct position, they are polarity specific, if backwards they would retard any voltage from getting to it’s destination. An LED & a standard Diode are a once way path for electricity, so they are polarized.
It is very easy to put them in the wrong way at times, been there, still doing it…
(Test, test, solder, test, re-solder, repeat, test, re-test, etc.)…
If you would like, I can record & show a video of that exact GP35 in action, & have the DC Powerpack there to show the voltages.
Let me know, may take a bit to arrange it. But it can be done…
Thanks Chad. Well I believe I wired it correctly however I will lay it out again…I’d installed components on a small PC, not soldered. I am pretty sure the LEDs and diodes were in there, + - as per the schematic…but worth rechecking it. I’m a greenhorn with electronics but I do know the positive from negative of an LED.
The purpose of this circuit is what I don’t get. I was thinking this would somehow store the juice to keep the LEDs lit although the engine was stopped…I have read somewhere…still looking for that link…using capacitors to store power so the LEDs would stay somewhat lit after running the engine for a while. Probably dreamed it.(:
i had temporarily wired the PC board to the copper clip on top of the Athearn motor…and to a screw installed on the chassis. Previously hard wired this Athearn…if you’re familiar with them you know what I mean. It didnt stop it from running but it definitely reduced the power…so, assume i had something wrong…I’ll redo all of it just to be sure…and report. If wired accurately your saying the power drop should be minor? And I also assume no overheated bridge rectifiers?
love to see your Athearn project you mentioned in the other post…I have a feeling its going to take me a bit of trial and error to get it right. Your list of lighting for it…using separate leds for all that? Debating if for all those lights would separate LEDs be unmanageable or use the fiber optic filament to cut down LEDs? I’ve seen a 2 mm fiber used successfully for marker lights …2mm filament could also suffice for Athearn headlights, tail lights as the stock openings in the U30c are just about 2mm. The distance from led to light opening is short so light is still very bright.
Well, appreciate the feedback… If you got the time…love to see the GP in action…particularly whats going on the back end. but don’t sweat it.
That circuit is mostly right. Assuming you have wired it in accordance with your schematic, you ought to have 1.4 VDC across each bridge rectifier, and 2.8 VDC across the pair of them. If at full throttle you have 12 VDC across both bridge rectifiers, then either the motor isn’t turning, or the motor is shorted somewhere and that’s why the bridge rectifiers are getting hot.
Rule of thumb. If you cannot lay the back of your hand (or finger) on it for the count of ten, it’s too damn hot. This rule is good for just about everything electrical except incandencent la
Chad…sorry, last thought for today…I realize that I wired this to the motor in parallel…I think…after another look at the circuit it is supposed to be wired in series…between truck pick up and motor…I had it on the motor…could that be my problem?
Hey there Dstarr…got it. I’ll rewire. I admit I’ve never seen a u30b running away so you make a good point. In fact I can’t find a picture of the rear end of a U30C or U28c, no less a PRR unit under power. Back to the drawing board.
That circuit is old school. Designed many years ago for constant lighting using 1.5 volt light bulbs. Headlight in the loco and tender light for reverse. Someone modified it for LED’s. The users back then knew it reduced the voltage to the motor by about 1.4 volts for each bridge, total of 2.8 volts for two bridges, but many power packs could get by that much voltage drop anyway. To my knowledge, that was never and issue. Maybe today it is.
Unless the motor is drawing a lot of current, the rectifies should not get very hot. Many used 1 amp bridge rectifiers and the motors did not draw over 1/2 amp. As I recall, many used can motors, not high amp open frame.
Did you measure the actual current?
At the time, a 1.5 volt bulb was placed across each bridge.
The author of the website http://www.awrr.com/ConstantLighting.html claims a 4-5 volt drop if using white LEDs or 2.8-3 volts using yellow. Scroll down to “The price you’ll pay”.
No thanks,
I’ll stick with a couple of LEDs and 470 resistors.
in Diode terms, (whether a regular or Light Emitting) they are polarized, the schematic shows 2 rectifiers, or Diode boxes. Those circuits create a polatrity balance, the arrows with a bar show the direction of voltage travel: >| means the voltage will go through from the left, to the right, will be stopped from the right to the left. Meaning you now have a directional flow.
However, LED’s are diodes that can only be activated by voltage in the right direction, so they do that without the bridge, as folks said, this is probably a design for incandecesnt bulbs & adapted for LEDS.
Each Diode the voltage goes through has a cost of 0.7 volts to pass through that logic.
There are ready made diode bridges that you can get to avoid making a big array shown in the schematic.
Also, this setup would work in DCC as it would pass the the opposing voltages, BUT the Reverse & the Headlight would both be on at the same time, due to it being AC voltage, & as we know it: DCC …
I hope that helps a little, it can get complex…
I think your heat issue is either an amperage one (you are putting motor balance current through the Diodes, or a wiring one). I know that in the early days, I accidentally wired a premade unit in parallel to the motor, (not in-between the pickup & motor, in series), & melted a spot on a locomotive shell, as it was trying to process all that motor current…
Make sure it is in series with the motor, not bridged across it.
Good luck! (PS: Looking for that Athearn BB/RTR loki to try a writeup on)…
Later,
Rich…I didn’t get a chance to measure the amps but like you said its old school…I’m done messing about with it for the moment…except to give it one more test…wired in series. But just to satisfy my curiosity. I can see what the intent may have been…in the old days as you’ve said. I just couldn’t understand what the purpose of this circuit was…it doesn’t do anything beyond what a led and resistor do.
Jim…LEDs + resistors…works for me…
Chad…I hear you. As a guy that returned to the hobby just this last year after 23 years away, making this sort of mistake provides the best training in how to do it right. There have clearly been significant advances in model RR’ing and I’ve got much to learn. Missed them all. So, I realize the complexity of this circuit, or just how complex it can be but that is exactly why I enjoy the hell out of it…these older Athearns make good test cases and I may even get a few sweet PRR diesels out of it for very little investment. I wish I could get my hands on one of those Athearn light boards just to see what is doable with it. Ill end up getting a RTR Athearn and pulling the board out for my old Athearn if I can’t find the boards alone. I’m not opposed to making this as simple as possible.
Well should you find your BB specials…let me know.
