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I am trying to setup some LED lights to run from the 9v track or a 9v battery pack for some train signals. I have 1.5v lights and the track is 9v (obviously) how can I step down the voltage. Any help would be great. (17 years ago, 16-Aug-07, to lugnet.trains)
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(...) Ideally, we'd need to know the current for the light you want to run. Even then,I can't remember the exact formula, but this page should help: (URL) :) (17 years ago, 16-Aug-07, to lugnet.trains)
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(...) dropdown resistance = (supply voltage - required voltage) / required current (in Amps) (17 years ago, 16-Aug-07, to lugnet.trains)
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"L. Andrew Reynolds" <andrew_reynolds@uhc.com> wrote in message news:JMvuv7.AF2@lugnet.com... (...) Typically, most LEDs have a mA rating of around 20mA. Let's assume this is the case for yours as well. I have seen some 1.5v LEDs so I 'm taking (...) (17 years ago, 17-Aug-07, to lugnet.trains)
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Yes Thank you very much. This is a big help I am electrically challenged in circuits. I am trying a Microwave switch to power a train signal and track for a manually movable bridge. I will try to post it later L. Andrew Reynolds (17 years ago, 17-Aug-07, to lugnet.trains)
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(...) Let me check I understand the theory of this - you want 1.5V across the LED, which means the resistor has to take the other 7.5V. You then pick a resistor that gives you a 20mA current at that figure of 7.5V. Then you double-check the power so (...) (17 years ago, 20-Aug-07, to lugnet.trains)
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"Jason J Railton" <j.j.railton@btinternet.com> wrote in message news:Jn2wvH.BoL@lugnet.com... *snip* (...) You are correct, In your case (assuming those LEDs are 1.5v and not your typical 2.1v variety), Vl would be 1.5v + 1.5v, or 3v So in our (...) (17 years ago, 20-Aug-07, to lugnet.trains)
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(...) I realize that this is an old post, but I jut found it...If I want to hook up a bunch of LED's (say they are 2.1 volt and I want to hook up 10) to a 9v system, what do I need to do? Only hook in four at a time or something like that? I could (...) (16 years ago, 22-Oct-08, to lugnet.trains)
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(...) For the DIYers out there: (URL) LED Resistor Calculator> For quick results without having to think: You can run 1 (2.1v) LED from 9v if you hook up a 390 ohm (1/4 watt) resistor between one lead of the LED and the power source. You can run 2 (...) (16 years ago, 22-Oct-08, to lugnet.trains, FTX)
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(...) I appreciate the links and information. I was looking at your stuff before (VERY cool) I posted, but I have always wanted to mess with this type of stuff. You have some neat stuff and I will probably come knocking at your door when I (...) (16 years ago, 22-Oct-08, to lugnet.trains, FTX)
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(...) If the voltage is going to vary, don't use a resistor as current source, consider a current regulator instead. That way the LED stays brightly lit over a wide voltage range without getting burned out at max voltage. This works for one or more (...) (16 years ago, 24-Oct-08, to lugnet.trains)
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(...) Great idea. I hadn't thought about whether Tom was going to use a variable speed control. I just assumed batteries for some reason. Have you had any brightness issues with the seemingly low 15mA output for multiple LEDs or are you hooking 1 to (...) (16 years ago, 24-Oct-08, to lugnet.trains)
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(...) Hey Rob, It would be safer to place a regular doide in series with this if the voltage is going to be reversed some of the time. But the circuit shown in the link handles reverse voltage up to 9v fine. The LED acts as a reverse protection (...) (16 years ago, 24-Oct-08, to lugnet.trains, FTX)
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I appreciate all your suggestions. Is there a website you can suggest that has more information on this stuff? Also, beside Jameco, what are some othe good places to buy parts? Thanks, Tom (16 years ago, 25-Oct-08, to lugnet.trains, FTX)
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(...) Farnell, Sparkfun, DigiKey, Radio Shack (Tandy/Dick Smith for AU crowd), Mouser (16 years ago, 26-Oct-08, to lugnet.trains)
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(...) As a crazy idea, use a MAX882/3/4 configured to output the required voltage. It is a step-up regulator that will work with as little as 1.5 volts. There are also PWM solutions. (16 years ago, 26-Oct-08, to lugnet.trains)
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(...) THANK YOU! (16 years ago, 2-Nov-08, to lugnet.trains)
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