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Sorry if you are seeing this as a crosspost from the robots tribe, I am a bit desperate for help!
I need to strobe a batch of LEDs, ideally 200, and need to use my DMX system to do so. I have a dmx strobe control unit, however it is only designed to trigger strobe lights using a 10 volt square wave with maybe a total of 250 milliamps available before voltage starts to drop off, possibly then damaging the controller.
250 miliamps will of course not drive a batch of 200 LEDs that will need, by my calculations, about 6 amps. (30ma x 200= 6,000ma)
I have no experience with using transistors in a circuit. Is it possible to use a transistor in a very simple homemade circuit, triggered by the 10V square wave, to switch the LEDs from a larger power supply?
Is the relationship between input and output voltages critical? If so, are calculations difficult?
Also, I understand transistors have a frequency limit to their switching, I think most should have no problem switching at a max rate of 20 cycles per second, is that a correct assumption?
Any advice you guys can give would be greatly appreciated.
I need to strobe a batch of LEDs, ideally 200, and need to use my DMX system to do so. I have a dmx strobe control unit, however it is only designed to trigger strobe lights using a 10 volt square wave with maybe a total of 250 milliamps available before voltage starts to drop off, possibly then damaging the controller.
250 miliamps will of course not drive a batch of 200 LEDs that will need, by my calculations, about 6 amps. (30ma x 200= 6,000ma)
I have no experience with using transistors in a circuit. Is it possible to use a transistor in a very simple homemade circuit, triggered by the 10V square wave, to switch the LEDs from a larger power supply?
Is the relationship between input and output voltages critical? If so, are calculations difficult?
Also, I understand transistors have a frequency limit to their switching, I think most should have no problem switching at a max rate of 20 cycles per second, is that a correct assumption?
Any advice you guys can give would be greatly appreciated.
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San Diego
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Re: Electronic circuitry help, transistor as a relay/switch
Wed, March 22, 2006 - 7:33 PMOops, I left out some of the info you might need.
The LEDs are rated at:
3.2 to 3.6 volts
80 milliwatts
30 milliamps
max peak forward current 75 milliamps
Thanks again for your thoughts and help! -
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Unsu...
Re: Electronic circuitry help, transistor as a relay/switch
Wed, March 22, 2006 - 8:00 PMI have been strobing LEDs very successfully with solid state relays. These are essentially the transistor switch you want with all the electronics sorted out for you. Take a look at www.jameco.com Part #176656 Make sure you get one that is DC in and DC out. You are correct that they have a frequency limitiation, but 20Hz is no problem.
200 discrete LEDs are kind of a pain to deal with. By the book, each one should have a current limiting resistor. But if your strobe pulses are short, you may get away without them. If you want some other ideas on how to get the same results with fewer and heavier duty LEDs, let me know.
Good luck. -
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Strobing LED's
Thu, March 23, 2006 - 8:09 AMCan you tell me more about how you are doing this?I am looking for a large bank of small strobes and have only been able to find curtain stobes at $12-$14 apiece-way too much.
How did dat ting dat you did?
Terry -
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Unsu...
Re: Strobing LED's
Thu, March 23, 2006 - 10:00 AMWell, let me start by saying that I got into this more from a science angle and then started using them for art photography. I'm not really familiar with DJ equipment or curtain strobes or what the ultimate goal is for your bank of strobes.
SHort version of what I am doing is this: using these high flux LEDs www.lumiledsfuture.com/produc...ily.cfm
They are much more powerful than what you are used to in a regular LED package, and much higher current draw. I switch them on and off with the solid state relay, as mentioned in previous post and I control the whole thing with a PIC micro-controller that I program myself.
LEDs still can not touch Xenon strobes (the usual DJ kind) in terms of light output, but doing this with the LEDs gives me control over pinpointing the light sources, pulse width, frequency rate and various other things, which are cool for me, but may not matter much for DJ purposes.
Good luck -
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Thanks..........
Thu, March 23, 2006 - 10:45 AMWell,I have many uses or this.
One is to decorate the effigy at Burning Flipside-the Texas Burning Man,but there are plenty of other applications too.
Thanks for your help.
Terry
www.westofdread.com
www.southdowns.org
www.artcarball.com
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Re: Electronic circuitry help, transistor as a relay/switch
Thu, March 23, 2006 - 6:33 PMP.J., thank you, thank you, thank you!
You solved all my problems and more! -
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Unsu...
Re: Electronic circuitry help, transistor as a relay/switch
Thu, March 23, 2006 - 10:03 PMMy pleasure, gentlemen. I have been spending a fair bit of time on this subject lately, and it's not something most people give a crap about. It's also a pleasure to post to a tribe thread that doesn't dissolve into name-calling ;-).
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Re: Electronic circuitry help, transistor as a relay/switch
Fri, April 7, 2006 - 7:50 PMSolid State Relays (SSR's) are the way to go. One alternative for connecting the LED's would be as a series string fed from a higher voltage DC power supply. This would require a higher wattage currecnt limit resistor. I have lit up LED series strings from rectified USA mains voltage and a high voltage filter capacitor (from an old tube based condenser microphone power supply). This worked very well.
