Anuther lektwonix kwestyun

[MChalkley]

I'm on a real "take more than I'm giving" roll on TBN lately, so in the interest of continuing that trend, and futhering the visibility/safety of my flashers on my EF-5, I'd like to ask the resident electronics gurus (Al, are you out there?) another question.

I mentioned in the thread on strobes that Bob started that Whelen has a "pulser" module for flashers. I'm not exactly sure what it does, but I suspect it produces 3 or 4 flashes a little longer than the "persistence of vision" duration (what is that, 1/23 of a second or so? I forget...), interspersed by off cycles of about the same duration, followed by the balance of the 2-second-or-so on cycle, followed by a 1 second or so off cycle, then the whole thing repeats.

Obviously, you can't do this with an incandescent bulb, because they aren't fast enough. My question is: How tricky is it to design a circuit to do this? And how much would the parts cost? Ok, that's two questions, but you guys have never been strict on that before...

 

[TWINKLE_TOES]

Mark,
<font color=blue>Al, are you out there?</font color=blue>

Well, just barely. I'm about ready to fall asleep waiting for 100K. Most strobes use a xenon tube and a trigger transformer to discharge a high voltage capacitor (300-400v) into the tube. Just like the flash on your camera, just runs periodically. I have built several when the kids were into launching rockets. Circuitry is simple and you can buy kits, Edmund Scientific and others for less than $20. I don't know anything about a "whalen".
Al

 

[MChalkley]

Whelen makes a lot of lights for emergency vehicles. But one of their options, and I don't know what they charge for it, is a pulser-flasher like I described that works with any kind of LED light. It's not a strobe, but it generates a strobe effect, just by pulsing the output to the LED. At least, that's what I think it does, based on a description I saw somewhere on their web site.

 

[Anonymous Poster]

<A target="_blank" HREF=http://strobeguy.safeshopper.com/specials.htm?210>Strobes & More...</A>

Flash 3 Headlight flasher

Product Details Stock #: Flash 3

The FLASH-3 does a standard back and forth wig-wag type pattern at a rate of 3 flashes per second.
Special: $35.99

Mark,

Here's something that may work with your nicely designed and existing rear light array...
{and you can still add some Whelen strobes...}

 

[TWINKLE_TOES]

Mark,
If all you want to do is pulse your LED lights in a strobe fashion that is no big deal for just LED's, but I think you mentioned that they had some other stuff in the light which allowed a constant illumination across a broad voltage range. In that case it may not be quite so simple. I have built a fish finder the mimics the operation of the old style neon light rotating on a motor. In that application to get a reasonable amount of light output I pulsed the LED's at 5 times the rated current but a very low duty cycle.
Al

 

[RPM]

I'm guessing the fancier ones have an IC in there to control the timing also. If I remember my personal ancient history there may be a few calculations necessary to get the right capacitor for the circuit - otherwise you won't get flashes of uniform brightness on the strobe - i.e. need to take into account how quickly the circuit charges before you can discharge it again.

A bit more trickery with the IC and dip switches would allow you to control how many pulses in a group and the time between groups.

My electronics knowledge is dusty though. Best bet is a local enthusiast that has a permanently warm soldering iron. Components would be cheap - it's just a niche application.

Patrick

 

[TWINKLE_TOES]

RPM,
<font color=blue>Best bet is a local enthusiast that has a permanently warm soldering iron. </font color=blue>

Well put, and sound advise /w3tcompact/icons/smile.gif
Al

 

[MChalkley]

Twinkle_Toes - Hmm. /w3tcompact/icons/hmm.gif You're right - I had forgotten about the internal circuitry. All it is though, is a power supply circuit. It ensures constant voltage at to the LEDs, as long as the input voltage is between 8 and 32 volts. So it shouldn't be affected by pulsing the input voltage, as long as it was a "digital", or square wave pulse, right?

 

[TWINKLE_TOES]

Mark,

<font color=blue>So it shouldn't be affected by pulsing the input voltage, as long as it was a "digital", or square wave pulse, right? </font color=blue>

That should be right, so long as the supply has no energy storage (capacitors) of consequence. Give it a try by touching the hot lead to the battery lead and see if the LED illumination follows the contact bounce.
Al

 

[MChalkley]

Al - It appears to, but I'm not exactly sure what I'm looking for. When I was messing with them earlier to take the pictures, they snap right on, and if you scratch the lead across the terminal, they flicker very quickly.