A critique needed

[charlie_r]

Hmmm. Maybe I need to attach a video of them actually working?

Most other forums I belong to ask that you upload your images to a host and link them. That is why I was doing that.

View attachment 61174

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Is that better?

By the way, I am only doing 2 in series of the white. I may go with 3 in series of the red or yellow/amber. However, I have NOT burned any out with only 1 LED wired to each transistor, and left it running for 48 hours. My guess is that the current rise time is what is limiting the current, as in doesn't have time enough to rise to unsafe levels.

 

[audioguru]

Thank-you. Now all of us can see your schematics for years and we don't need to wait and wait and wait for PhotoBucket to wake up.

Transistors are not identical. They have a fairly wide range of current gain. Some will have a high output current which will burn out your LEDs. Maybe you are lucky that your transistors have low gain.

Why are you talking about rise-time? Your LEDs turn on then turn off slowly.

 

[charlie_r]

I will borrow a video camera and post to show you that the timer setup I have built flashes the LEDs. It does NOT slowly turn on then fade off.

Think square wave not triangle or sawtooth or ramping on and off.

 

[audioguru]

If you switch the LEDs on and off at 1kHz or more then they will be ramping.

 

[charlie_r]

I am switching them at one hertz not one kilohertz. One flash per second.

If I wanted a fade in and out, I would not be using a 555. A pair of transistors and caps would do the job better for that.

Please go back to the top of this thread, and re-read.

 

[charlie_r]

I am resurrecting this thread, just for AudioGuru.

Here is a video of the light system on my trike, to show you that my LEDs DO strobe, not ramp up and down.

https://youtu.be/z2oWy19VzBk

 

[audioguru]

The on-time of the strobes is too short to be seen properly in a video.
Since nothing except the low current gain of the transistors limits the current when the transistors are cool then the LEDs might burn out in summer when the transistors will have more current gain caused by heat.

How did some of the turn signals LEDs burn out? How are you ramping them?

 

[charlie_r]

The turn signal burn out....

5 LEDs in series with current limiting/balancing resistors (5% tolerance), 10 sets in parallel, cheap non binned chinese LEDs. Actually expected a few like this.

Being run by a 555 and buffered by a 3709 pnp current sink. no ramp time there either, it's either full on or full off.

Instead of running individual transistors on the strobes, I went with a uln2003 sink array.

I checked for possible heat issues by running several sets of strobes on a piece of stock warmed to ~110F, roughly equal to our normal summer highs. However, you do bring up a good point about the current sink uln2003, so I will be watching it as the weather warms up.

This is a pic of the strobe control board, as attached to the trike. If I have heat issues with it, I will move it into the airflow under the seat. Yes there is a second socket for another uln2003 if I decide I need to add more channels. That is a option to reduce the heat load per each channel, by paralleling channels. The datasheet suggests this method for driving more than 350mA constant current. As this is pulsed, each channel is handling an average over time of ( I think ) ~ 8mA, if my math is correct....current divided by pulse duty cycle??? At any rate, the array doesn't get any warmer than ambient.

View attachment 62765

Another possible explanation for no burn out on the strobes -- I'm running 28AWG wire rescued from an old parallel cable. Probable current limiting from that, due fully to the small wire size. However, I have run close to an amp through wires that small in other applications.

 

[audioguru]

In the video, the turn signals appear to fade up and fade down like big incandescent light bulbs, without the abrupt ON and OFF that happens with LEDs on cars.

 

[charlie_r]

Probably an anomaly from the relatively inexpensive digital camera. 30fps is the best it can do. I know, cameras don't record exactly what we see.

 

[kinarfi]

My legs propel my trike. It is an AtomicZombie.com loderunner.

To the heat problem: with an extremely short duration, these LEDs are not showing any signs of heating. I've been running a set of 8 --2 per channel-- for the last two hours here beside me, even the pair that are not on stars seem to be staying cold. One of the things I've noted in my research is that you can overdrive LEDs to close to 75% above their constant rating, as long as you have an extremely short pulse duration with a relatively long off period. Ostensibly to give the die time to cool off between pulses.

For the xenon tubes: as stated before, I doubt they would be as reliable as the LEDs, given the conditions they will be subjected to. That, and I'm not too crazy about getting a few kV+mA shots up my pants should something go wrong with them. Would tend to knock me off the seat.

Reloadron, according to the alliedelec.com website, it appears to be an order it in component with a lead time of 8 weeks. or maybe I went to the wrong website? same results going to allied electronics website.

https://www.alliedelec.com/search/s...onSearch=D:IRL3302,Dxm:All,Dxp:3&SearchType=0

go direct to IR,
**broken link removed**

 

[Reloadron]

Reloadron, according to the alliedelec.com website, it appears to be an order it in component with a lead time of 8 weeks. or maybe I went to the wrong website? same results going to allied electronics website.

I have several sitting here and as I mentioned if you want one it's yours for the asking. I'll mail it to you postage paid as in totally free.

Ron