LED board?

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elec_mech

Joined Nov 12, 2008
1,500
Okay, I've just about finished a bill of materials. Couple questions:

  1. What color do you want the LEDs to be?
  2. How tall do you want the digits to be?
  3. Do you want a light to indicate when the circuit is on like the OP did?
  4. If yes to 3, do you want a separate LED like the OP used or would a lighted switch work?
 

imakehp

Joined Aug 26, 2013
11
1. First choice blue....2nd red
2. First choice 4"....2nd 4.5"....3rd 5"
3. Something on the dash by the thumb wheel number controller would be nice. But not absolutely necessary to me. Although it might become an issue because I won't be able to see the board when strapped into the dragster. Perfect for me would be a small (.5"-1") display on the dash of what numbers are showing outside on the board. BUT don't let that feature become a hassle to you. I can reach in the drivers compartment and set/check what the board is showing before putting my firesuit on and strapping in to make the run.
I'd be glad to PM you my cell # if you'd prefer to clarify some of these details.

Thank you VERY much for your time on this......

Dave
 

imakehp

Joined Aug 26, 2013
11
I just remembered something about the thumbwheel thing having numbers on the the wheels themselves.
If so, the inside display would just be a luxury I guess and not necessary. :)
 

elec_mech

Joined Nov 12, 2008
1,500
Blue LEDs require more forward voltage than red. Due to the 12V limitation, this means we either need to put some LEDs in parallel for each segment and risk having them look uneven in brightness or use less LEDs to make a segment. I've attached a drawing for a 4" tall digit using three LEDs for each segment. It is made to scale, so you can print it and see what you think. Let me know if this is acceptable or not. The OP used 4- and 5-LED segments, but I'm not sure how it was wired.

Yes, the thumbwheel dial has numbers on it, so no need for another display (this is much cheaper and easier which is why these were selected originally). If you're using this at night, you could add a small piece of acrylic and shine a couple of white LEDs at the ends to light the thumbwheel digits.

You can of course make a digital display, but again, more time and money. Perhaps an upgrade later?

To clarify, the thumbwheels should be seen and adjustable from the driver's seat. The OP just showed them next to the LED display to get them into one photo. There will be a cable from the switches to the display. Still working out how best to do that. Tentatively thinking of a DB-15 cable, but I'll have to see if the wire size will handle the current requirements.

Will this be used mostly during the day or night or both? Daytime use requires the LEDs be brighter to overcome sunlight while nighttime requires the LEDs be dimmer so they can be read without blinding someone.

Are you going to take care of finding a suitable enclosure for the display and thumbwheels or would you like some suggestions? The OP appears to have had a custom box made from sheet metal for the display.
 

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imakehp

Joined Aug 26, 2013
11
Blue LEDs require more forward voltage than red. Due to the 12V limitation, this means we either need to put some LEDs in parallel for each segment and risk having them look uneven in brightness or use less LEDs to make a segment. I've attached a drawing for a 4" tall digit using three LEDs for each segment. It is made to scale, so you can print it and see what you think. Let me know if this is acceptable or not. The OP used 4- and 5-LED segments, but I'm not sure how it was wired.

Blue leds are best for me, but red are OK if much easier.
Digit size in pdf is xlnt.
Curious if led's will look "pinpoint" like drawing or will they "blend" together more?

Yes, the thumbwheel dial has numbers on it, so no need for another display (this is much cheaper and easier which is why these were selected originally). If you're using this at night, you could add a small piece of acrylic and shine a couple of white LEDs at the ends to light the thumbwheel digits.

I'll take care of illuminating the controller on the dash.

You can of course make a digital display, but again, more time and money. Perhaps an upgrade later?

Yes, let's get something in the car and working for now and improve if needed later.

To clarify, the thumbwheels should be seen and adjustable from the driver's seat. The OP just showed them next to the LED display to get them into one photo. There will be a cable from the switches to the display. Still working out how best to do that. Tentatively thinking of a DB-15 cable, but I'll have to see if the wire size will handle the current requirements.

Yes, controller inside on the dash by me.


Will this be used mostly during the day or night or both? Daytime use requires the LEDs be brighter to overcome sunlight while nighttime requires the LEDs be dimmer so they can be read without blinding someone.

Unfortunately, both day and night racing. I don't think excessive brightness would be an issue. The board has to be seen by the tower which is anywhere from 50' to 80' away.

Are you going to take care of finding a suitable enclosure for the display and thumbwheels or would you like some suggestions? The OP appears to have had a custom box made from sheet metal for the display.

I have a very good stainless steel fabricator that will make the enclosure for me.




Man, this is exciting!!! Thank you VERY much for your time and effort, and again I don't expect this for free.


Dave
 

elec_mech

Joined Nov 12, 2008
1,500
Curious if led's will look "pinpoint" like drawing or will they "blend" together more?
Unfortunately, both day and night racing. I don't think excessive brightness would be an issue. The board has to be seen by the tower which is anywhere from 50' to 80' away.
If time allows, I'll make a single digit like this and "see" how it looks at 50' then at 80' away in daylight. On hindsight, blue is about the best color you can select for viewing in daylight by the way. How tall is the tower? Is the 50-80' accounting for the tower height or is this just the distance between the car and the base of the tower (ground level distance)?
 

imakehp

Joined Aug 26, 2013
11
The towers vary from track to track, but most are 2-3 stories tall. The 50-80 foot estimate is a ground level measurement. So viewing angle would be from 20-30 feet up.
 

elec_mech

Joined Nov 12, 2008
1,500
Hmm, not sure how well someone could see a 4" display from 2-3 stories high and 50-80' away, but we'll see. I made a 3-LED segment, 4" display. Will take some pictures from ground level 50-80' away in daylight. This should be interesting.
 

elec_mech

Joined Nov 12, 2008
1,500
Hmm, performing some trig, at a distance of 80' and say 26' high (two stories plus a 6' tall person), distance to the display is about 84'. I took a picture with a zoom to approximate how well I could see from that distance. It was supposed to show a four, but segment c got shorted out, so all you see is a u.

I used 6000mcd blue LEDs with a 10° viewing angle running at ~20mA. While you can just make out the u if directly facing the LEDs, the display all but disappeared if they moved or if I wasn't at just the right angle. This will be helped quite a bit by using LEDs with a wider viewing angle with a higher mcd rating.

Also, using 3 LEDs per segment is pushing it a bit, so looks like 4 or more is the way to go. Not hard to implement, just not as simple and elegant as I was hoping for.

I think using 4" tall digits at that distance is probably okay, but 5" would be easier to read if you got the space in your window.

If you do a double row of LEDs for each segment, reading the display will be even easier. This will add more cost, but it will look cooler too.
 

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imakehp

Joined Aug 26, 2013
11
If you're saying that photo is from 80' away, whatever size that is, would be fine. I think a mechanical, or digital look would fit in perfectly in a racing environment. I race a dragster so the display will be on a bracket mounted by itself out in the open. Also, would the led numerals look more diffused or solid if mounted behind colored/tinted plexiglass? Just curious because from your photo it looks perfectly fine as is to me. But, you're standing in front of it so I defer to your judgement(s).
 

elec_mech

Joined Nov 12, 2008
1,500
Also, would the led numerals look more diffused or solid if mounted behind colored/tinted plexiglass?
The digits would be easier to read up close behind a dark or tinted Plexiglas because it would help hid the unlit digits. At a distance of 80'+, it probably wouldn't make much difference. It would appear more polished in overall appearance though.

As another member pointed out to me, you also have to keep in mind that a cover is potentionally a reflective surface, so if the display is read in the sunlight or bright stadium lighting, the cover could reflect the ambient light making it hard or impossible to read the display at certain angles. One way around this is to use a material designed to be non-reflective. The member mentioned used a thin Plexiglass cover designed to go over pictures in picture frames with the diffused side facing outward. This blurred the display a tad, but helped against glare from office lights. I haven't experimented with this yet.

If you're not in a hurry, I can purchase a few LEDs from different suppliers and perform some tests with different outputs and angles and perhaps filters to see what might work best.
 

elec_mech

Joined Nov 12, 2008
1,500
Just a quick update - I ordered several blue LEDs with different viewing angles and intensities to "see" which can be viewed from a distance and at what angles. I've put together a display showing each type next to each other. I've wired 4 of 5 - one to go then I need to add resistors and I'm ready to commence testing and will post the results. Got a lot going on at home, so tentatively planning to have results late next week. Stay tuned . . .
 

imakehp

Joined Aug 26, 2013
11
XLNT!!!!! Thank you mech...

Remember not to over think this....all it has to do is display 3 numbers reasonably clear. Manipulating the display from inside the dragster is a bonus of course and will make these more sellable if we, I, you decide it's something we can market. I'm just thinking "what if" in regards to that. :)

Thank you again for your time and effort...

Dave
 

elec_mech

Joined Nov 12, 2008
1,500
Remember not to over think this....
Ha-ha. Then you've asked the wrong person for help. :D No worries, I'm not adding or changing the circuit itself. I still need to give some thought to a switch enclosure and wire connections, but not much effort is required beyond that.

So you are considering marketing this? Are you thinking of selling it as a kit, a finished (assembled) product, or both?

....all it has to do is display 3 numbers reasonably clear.
That's all I'm focused on at the moment. LEDs come available in different intensities and viewing angles. I want to see what characteristics would be best for this application. This will also help me expand on my growing knowledge of LEDs as I've been a part of several LED display projects on AAC. To save money, I bought from eBay, but as most came from Asia, it took several weeks to get, hence the radio silence, so to speak. Now I've got everything and I'm moving forward as time at home allows.
 

csnead

Joined Oct 7, 2013
6
Hello everyone! I am new to this forum, but I would definitely be interested in one of these diy type kits. I could also help with the project if you decide to market it! :D
 

elec_mech

Joined Nov 12, 2008
1,500
Okay, finally got the LEDs in, build a mock display, tested outside, took pictures and now posting results. All LEDs were feed with about 20mA to compare apples to apples.

Sorry, gotta head out the door, so apologize for haphazard writing in advance.

I bought several LEDs from eBay with different intensities and viewing angles. Because you want to see the display from angles as well as head-on, the larger the viewing angle, the better. Unfortunately, you can only get so much intensity at a wide viewing angle which can reduce your effective viewing range, so there is a tradeoff.

So looking head-on, they all look great. At a roughly 45° angle from center, the ~25° LEDs all but disappear. The 100° LEDs, naturally, do much better. Of the 100° LEDs, I had two - one a standard 5mm diffused LED and a superflux. The diffused is hard to see in daylight, the superflux no problemo.

In the dark, all LEDs are almost blindingly bright. This can be reduced with different resistors.

So, assuming you go with the 100° LEDs, the diffused 5mm LEDs will be easier to put into a material such as 1/8" thick acrylic or sheet metal. The superflux will require a PCB unless you want to do a lot of gluing. I'll look and see if there are any superbright 100° standard 5mm LEDs in the meantime.
 

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