miditron controlling LED greater than 5v?

Jan 18, 2007 at 12:17am

miditron controlling LED greater than 5v?

is it possible to control an LED whose voltage is great than 5 with a miditron (which normally outputs 0-5v) Is there some kind of hardware i can buy to allow this? I just got max/msp two weeks ago, and I’m doing ok, but I have very little knowledge of were to start in terms of controling lighting via MIDI/audio. A class in robotics and kinetics i signed up for just got cancelled so I really could use the help guys!
Thanks again,
-MAX

#29768
Jan 18, 2007 at 12:31am

what sort of voltage does it require? you can use a transistor (like
a tip120) with a higher voltage supply, and use the miditron as a
digital switch.

tom igoe’s notes, and the itp physcomp pages in general, will probably
have, at the very least, pointers to information you can use :
http://tigoe.net/pcomp/relay-transistor.shtml
http://tigoe.net/pcomp/index.shtml

http://itp.nyu.edu/physcomp/Intro/HomePage

~s

On 1/17/07, M. Abeles wrote:
>
> is it possible to control an LED whose voltage is great than 5 with a miditron (which normally outputs 0-5v) Is there some kind of hardware i can buy to allow this? I just got max/msp two weeks ago, and I’m doing ok, but I have very little knowledge of were to start in terms of controling lighting via MIDI/audio. A class in robotics and kinetics i signed up for just got cancelled so I really could use the help guys!
> Thanks again,
> -MAX
>

#93562
Jan 18, 2007 at 12:33am

First question: why are you using an LED with greater than 5v forward
voltage? Most top out at around 3v.

If you need to drive any dc device with higher voltage, simply use a
transistor driving circuit. The schematic in the MidiTron manual (at
http://miditron.com) for driving a motor will work (though you won’t
need the 1n4001 diode and can probably use a smaller npn transistor,
depending on the LED’s current requirement).

Eric

At 5:17 PM -0700 1/17/07, M. Abeles wrote:
>is it possible to control an LED whose voltage is great than 5 with
>a miditron (which normally outputs 0-5v) Is there some kind of
>hardware i can buy to allow this? I just got max/msp two weeks ago,
>and I’m doing ok, but I have very little knowledge of were to start
>in terms of controling lighting via MIDI/audio. A class in robotics
>and kinetics i signed up for just got cancelled so I really could
>use the help guys!
>Thanks again,
>-MAX

#93563
Jan 18, 2007 at 4:03am

what sort of voltage does it require? you can use a transistor (like
a tip120) with a higher voltage supply, and use the miditron as a
digital switch.

well, I actually want to be able to fade the sucker. Wouldn’t it make that impossible if the miditron was acting as a “digital switch?”

Huh, the lights i’m looking to use are 12 volt. I just realized that it is a small 2 pin (?) bulb with 32 5mm LEDs. hehe. well, can this work with Miditron? I mean, i don’t need a big DMX theater lighting setup, but I’m trying to light the indside of a transperent sculpture, and a little LED won’t do s*** in the grand scheme of these. I want multiple lights triggering at different times possibly inside the same form, so the small size of LED’s are good…….i really don’t know what i’m talking about. But if this clarifies anything and you guys can throw some answers that would be wonderful. I will check the links you both gave me now. Thanks
cheers, tears, yet I persevere!!
-max

#93564
Jan 18, 2007 at 4:31am

you will need to pwm the leds if you are using a microcontroller and
want to fade them. it’s a pseudo-analog output since
microcontrollers, being digital, can only spit out digital signals.
see more here :
http://www.embedded.com/story/OEG20010821S0096
apparently, there are pages in tht emiditron manual on pwm.. check
there as well.

On 1/17/07, M. Abeles wrote:
>
> what sort of voltage does it require? you can use a transistor (like
> a tip120) with a higher voltage supply, and use the miditron as a
> digital switch.
>
> well, I actually want to be able to fade the sucker. Wouldn’t it make that impossible if the miditron was acting as a “digital switch?”
>
> Huh, the lights i’m looking to use are 12 volt. I just realized that it is a small 2 pin (?) bulb with 32 5mm LEDs. hehe. well, can this work with Miditron? I mean, i don’t need a big DMX theater lighting setup, but I’m trying to light the indside of a transperent sculpture, and a little LED won’t do s*** in the grand scheme of these. I want multiple lights triggering at different times possibly inside the same form, so the small size of LED’s are good…….i really don’t know what i’m talking about. But if this clarifies anything and you guys can throw some answers that would be wonderful. I will check the links you both gave me now. Thanks
> cheers, tears, yet I persevere!!
> -max
>

#93565
Jan 18, 2007 at 11:30am

I don’t know about the miditron, but many interfaces I do know use a
“pull down” circuit to switch digital outs. This allows you to
connect the other end of your circuit (LED, relay, whatever) to
whichever voltage it needs. You just have to make sure your device
doesn’t need more current than the interface can sink. Have a look at
the instructions for the miditron to see if this applies. If not, you
need to add a transistor that is switched on by the output of the
miditron – make sure it is rated fro the current required by the device.

Best

L

On 18 Jan 2007, at 00:17, M. Abeles wrote:

>
> is it possible to control an LED whose voltage is great than 5 with
> a miditron (which normally outputs 0-5v) Is there some kind of
> hardware i can buy to allow this? I just got max/msp two weeks ago,
> and I’m doing ok, but I have very little knowledge of were to start
> in terms of controling lighting via MIDI/audio. A class in robotics
> and kinetics i signed up for just got cancelled so I really could
> use the help guys!
> Thanks again,
> -MAX

Lawrence Casserley – lawrence@lcasserley.co.uk
Lawrence Electronic Operations – http://www.lcasserley.co.uk
Colourscape Music Festivals – http://www.colourscape.org.uk

#93566
Jan 18, 2007 at 3:20pm

If you’re driving that many LEDs, you will definitely need a big
transistor. Check the current requirements of the light versus the
current rating of your transistor (which should at least be a
darlington in a TO-220 package).

Use the motor driving schematic in the MidiTron manual (deleting the
shunt diode). Use a 12v supply to the + of the light, and run the –
of the light to the collector of the transistor. Make sure the 12v
supply is rated with enough current to drive the light. Connect the –
of the 12v supply to MidiTron ground (in general, all your supply
grounds should be tied together in a multi-supply circuit such as
this).

Get it working in Digital Out mode, then simply switch the MidiTron
terminal to Analog Out mode. It will provide a PWM signal to the
transistor base, thus PWM-ing the light, which will effectively work
as a dimmer. This is how DC dimming is almost always done with
digital circuits.

Good luck!

Eric

At 9:03 PM -0700 1/17/07, M. Abeles wrote:
>what sort of voltage does it require? you can use a transistor (like
>a tip120) with a higher voltage supply, and use the miditron as a
>digital switch.
>
>well, I actually want to be able to fade the sucker. Wouldn’t it
>make that impossible if the miditron was acting as a “digital
>switch?”
>
>Huh, the lights i’m looking to use are 12 volt. I just realized that
>it is a small 2 pin (?) bulb with 32 5mm LEDs. hehe. well, can this
>work with Miditron? I mean, i don’t need a big DMX theater lighting
>setup, but I’m trying to light the indside of a transperent
>sculpture, and a little LED won’t do s*** in the grand scheme of
>these. I want multiple lights triggering at different times possibly
>inside the same form, so the small size of LED’s are good…….i
>really don’t know what i’m talking about. But if this clarifies
>anything and you guys can throw some answers that would be
>wonderful. I will check the links you both gave me now. Thanks
>cheers, tears, yet I persevere!!
>-max

#93567
Jan 18, 2007 at 5:57pm

OH wow, thanks for the wealth of responses. I shall go ahead and just purchase the miditron and finagle my way through the process, making sure NOT TO KILL MYSELF. ;) THANKS EVERYONE!!!!!
Cycling’74 makes some pretty inventive s***, eh?

http://www.youtube.com/watch?v=t_ClCw0e0Ow
this is a perfect example of what i’m looking to accomplish (in the short term)

-Max

#93568
Jan 18, 2007 at 6:41pm

At 10:57 AM -0700 1/18/07, M. Abeles wrote:
>OH wow, thanks for the wealth of responses. I shall go ahead and
>just purchase the miditron and finagle my way through the process,
>making sure NOT TO KILL MYSELF. ;) THANKS EVERYONE!!!!!
> Cycling’74 makes some pretty inventive s***, eh?

Not to toot my own horn, but it’s actually made by me :-) See
http://miditron.com for info and ordering.

Cycling’74 definitely makes inventive s*** though!

Eric

#93569

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