How to make an LED voltage indicator.

ThePsuedoMonkey

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OK, so was browsing around Amazon, ordering tools for my car, when a voltage indicator gauge caught my eye (the same one that I tried to attach to my bike last year). And I thought "yes, I would still like that information about my bike when I'm riding." Nothing I found really got me excited though, especially considering most were going for $40+. Then I started looking into DIY projects... and found only one that was simple and didn't require expensive, hard to find, or complex components. :mad:

Inspired by that find, I Googled an online circuit simulator and set to work with the specs of typical colored LEDs at my disposal. To me, there were only two acceptable outcomes: an easy to read and highly detailed model based on the number of LEDs illuminated, or a minimalist approach that spans the same voltage range and conveys the important information. I started with the OCD model, but my first attempts were less than impressive, since I was restricting myself to only resistors and LEDs. Retreating to the online radio shack, I picked out one of the zener diodes available and played with that. Eventually I ended up utilizing a little bit of each component to finesse my way toward the minimalist design. At it's most simple level, red=bad green=normal blue=good. It operates between 10V and 15V. The diagram is below, and the actual simulation can be used here.

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What you need to know:
-Two zener diodes (Zener Voltage=8.4, Forward Voltage=1.1) in series with the source voltage, and polarity is reversed on the second diode.
-Three different LEDs (Forward Voltage= 2.1, 2.9, 3.1 respectively for red, green, blue) share a node with the zener diodes.
-LEDs are in series with resistors (100, 100, and 300 ohms respectively).

I did my best to make it simple enough for a novice to do in an hour with under $5 worth in materials. Now I just need to think about a tasteful way to mount this!
 
post a pic when you get it mounted. Given the electrics on this bike it is nice to have info on the state of the charging system. I have a gauge on my bike but it doesnt like the vibrations too much
 
Wow, the thread got pushed to pg11! I need to finish things sooner. :laugh: Finally got the set of parts in the mail this week (yay ebay!) so get to finish this simple mod (I call 'em "softmods" now, since they are fairly minor things).

I borrowed my brother's test board, since I wanted to double check that everything was honky-dory before I got going. Lo and behold: not quite as expected. I ended up changing to a two diode setup; 9V on the red&blue and 10V on the green:
Voltage Indicator final.jpg
It works!
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Green is not as bright, but oh well. It still works after I attach magnet wire for power, too!
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Now I need some way of mounting it... found one of those multi-compartment case separators.
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Perfect! Then formed the base and set/waterproofed it with silicone. I wanted to do a mold for the silicone (for a more professional look) but it did not sand down well on my test sample. :(
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Not quite my color... Found some metal red from when I did the gauges/headlight/rear and dabbed some oil on the top of the LEDs. I had to remove the washers on those bolts, but I think the end result was worth it!
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I ended up tying power into a shunt I made (can't go ruining stock stuff yet!) through the brake circuit (powers with main), and tied into a random ground that wasn't used. It's pretty sweet, if I do say so myself: discreet and discrete. :D That circuit does have a lower voltage than the battery, but now that I know I can adjust my readings accordingly.
 
Wow, you need to market this, even as an assembled but ready to mount kit. I would love this on my bike but electricity and I aren't on good terms.
 
I know that feeling! Turns out the 3mm red LED didn't like that circuit. :rolleyes: I made a new one with 5mm LEDs and picked resistors that limit the current to 10mA (680 on the red and 270 on the others), so it should last this time. I probably wouldn't be very good at marketing a kit for this, dO-bOy but I could wire one up for you if you'd like!
 
why not use a tri-led, two LEDs in one and the third light is a mix of both. see it in action in my blog and I think my rewire how to.
 
why not use a tri-led, two LEDs in one and the third light is a mix of both. see it in action in my blog and I think my rewire how to.
I hadn't thought of that, it would work pretty well if I was able to work out an easy way of shutting off power to the leads. Looks like there are even RGB ones that have individual leads. That would definitely lean even more towards a minimalist design, so I may look into it.
 
I installed a tri-color LED on my last scoot. Came in a kit as a battery monitor. Mounted it on the dash under the glass (plastic) below the high beam indicator light. "Green" for charging, "yellow" for borderline and "red" for discharge. The scoot had the same minimalist charging system as our Yammys. Worked well and looked custom. There was s sticker that went around the LED indicating the key code of the colors. You could have installed just the LED. Wonder if one would fit in the stock light cluster?
 
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