LED gear indicator. Confirm my diagram, please?

[CrawlingForward]

Woot woot! This thing is going to be awesome.

After being very proud of myself with my first multi-LED draft, I realized that I had the potentiometer downstream of where I was switching the ground, meaning it wouldn't work on the bike and it would *have* to have the potentiometer upstream of all the LEDs, otherwise I'd be channeling all the grounds back to one again.

Basically, it was my original design, just with more resistors.

Basically, it ended up being:
12v-->potentiometer-->LED(s)-->high ohm resistor-->constant ground
|--->low ohm resistor-->switched ground

It took a lot of tweaking with resistors to make all the LEDs function on the same basic voltage curve and light output, but I got it as close as I think is possible.

White 3mm: Dim-22k, Bright-2.2k
Green 5mm diffused: Dim-680, Bright-68
Yellow 3mm: Dim-3.9k, Bright-470
Red 3mm: Dim-10k, Bright-470

The green diffused one really threw me off, as it required *way* more power for the same brightness. A 3mm non-diffused LED instantly blew when I swapped it in the circuit, so if I wasn't using the 5mm diffused, it would be much more similar to the rest.

Enough description: Video!
(The video is me running a ground connection across the ground leads from each LED)
https://www.youtube.com/watch?v=OzwLYd-YUhg

[Shawn68z]

Hope you don't mind alittle input on this. I have lots of experience with LED (I designed LED tail lights for transport trucks and school buses about 15 years ago)

Currently you have 1 470 ohm resistor for all 6 LED's. Thats not going to work properly. You need to have a serperate 470 ohm resistor for each LED. It comes down to voltage dividing, between the LED. The 470 Ohm is to control current, and drop most of the voltage (Vcc-0.7). That works fine for the LED that is currently selected (G5 in the example). So 25mA is going thru that part of the circuit. That part is fine. But once you turn on the other LED's its going to cause the voltage of the 470 resistor to drop, which will cause your G5 line to draw more current and fry the LED.

Depending on the LED you select, they will start emitting light around the 10mA point, and will max out around 30mA. I would recommend a 470 on the top for each (which gives you 25mA@12V,) and another 470 at the bottom of the resistor (instead of the 10K) to give you 12mA for non-selected. Then you can use the pots above the 470's ohm resistor to control all of them (between 12V, and the top of the 470's), and a pot at the bottom to control the non-selected LEDs.

Hope that makes sense, I will post a drawing later tonight when I get home from work.

Cheers,
Shawn.

[CrawlingForward]

Hey Shawn,

No, please! The more input the better. I'm in this to learn.

I couldn't tell from your post if I you had read the specs of the prototype, but I ended up putting independent resistors on each ground, which *seems* to be working (see video) with a single potentiometer.

I'll definitely try your recommendation out on the breadboard as well!

Question, though: So in the video above, everything works about how I'd like it to, but I'm only using like the top 1/4 of the pot range. If I wanted to take advantage of the full range for more granular control...could I do that by changing the potentiometer? Aka, it works with 0 ohms to 25k ohms (assuming a pot is linear. I have no idea on that front), so if I grabbed a pot that was like 25k or 30k or maybe 50k ohms, would that produce the same affect, but allow full use of the dial?

[Shawn68z]

I understand exactly what you are triing to acomplish with the circuit, and i think its a great idea. I have not watched your video as where I work blocks youtube.

Not all pots are linear. When I get home I will watch your video. The circuit that was posted earlier (post #6), is a good basis, but put 6 470's (on the top of each LED). If you want the circuit to flow a minimum of 10mA thru each LED when the POT is at max resistance, and to allow 200mA or so when turned all the way off.

The LED's that you are using, do you have the companies spec sheet, or are they just random LED's?

Shawn.

[trippivot]

DSC00632.jpg my gear position selector and neutral lights.

I bought different resistors to vary the brightness - and the different colors need different resistors to make the same them the same brightness - I first thought same resistor means same brightness. - nope and I still want to put a dimmer dial or switch for night and day -- each led gets it's own resistor, I use a negative switched signal.


you are definitely on the right track -- my notes got tossed but I fumbled it together enough to know what gear I'm in. 1st blue -- 3rd is red for burnout gear, the whole purpose was I hate hitting 5th gear twice. green is neutral.

[CrawlingForward]

[ATTACH=CONFIG]38156[/ATTACH] my gear position selector and neutral lights.

I bought different resistors to vary the brightness - and the different colors need different resistors to make the same them the same brightness - I first thought same resistor means same brightness. - nope and I still want to put a dimmer dial or switch for night and day -- each led gets it's own resistor, I use a negative switched signal.


you are definitely on the right track -- my notes got tossed but I fumbled it together enough to know what gear I'm in. 1st blue -- 3rd is red for burnout gear, the whole purpose was I hate hitting 5th gear twice. green is neutral.

Sweet! Glad to know I'm not the only who thought it was a cool idea.

I just ordered a couple more pots to experiment with. I'll let you know what I find!