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1  Using Arduino / General Electronics / Re: Converting a 5v transistor switch circuit to work with a 3.3v Arduino on: September 19, 2013, 08:45:39 pm
470Ω did it! Thanks!
2  Using Arduino / General Electronics / Re: Converting a 5v transistor switch circuit to work with a 3.3v Arduino on: September 19, 2013, 08:11:24 pm
Sorry, my engineering knowledge failed me there.


LED array is the following:



12V ----> 150Ω resistor ---> LED ---> LED ---> LED ---> transistor collector
       \-->  150Ω resistor ---> LED ---> LED ---> LED --/
3  Using Arduino / General Electronics / Re: Converting a 5v transistor switch circuit to work with a 3.3v Arduino on: September 19, 2013, 07:47:11 pm
Also, here's a post I made that might explain the circuit better http://forum.arduino.cc/index.php?topic=78137.0;wap2.
4  Using Arduino / General Electronics / Converting a 5v transistor switch circuit to work with a 3.3v Arduino on: September 19, 2013, 07:45:51 pm
Hello,

I have a transistor switch circuit driving an LED light array with PWM that is working great with my 5v Arduino, and I'm not sure how to modify it to work properly with my Teensy 3.0, which is 3.3v.

The circuit is like this:
                                                             collector ----> gnd of LED array ---> LED array ---> 12V
                                                           /
PWM output ---------> 1kΩ resistor ----> TIP29C base
                                                           \
                                                             emitter ----> gnd

What value of resistor would make this circuit work as a switch with a 3.3v PWM output?  It's been a couple of years since I've done these calculations...

Thanks to anyone that can help!

Drew
5  Forum 2005-2010 (read only) / Interfacing / MaxMSP midi clock to arduino on: March 08, 2010, 12:57:26 pm
Hello,

I'm trying to send a midi clock from Max MSP (originating in Ableton Live) to my Arduino to trigger lights, etc.  Can someone point me on the right path to start this?  I have some code to actually parse the serial data on the arduino and interpret the MIDI clock bytes and such, but I need to figure out how to actually send the MIDI data from Max to Arduino...


Any help would be much appreciated.
6  Forum 2005-2010 (read only) / Troubleshooting / Programming standalone Arduino in-circuit on: October 05, 2010, 02:44:38 pm
Hello,

I've set up my Arduino in a circuit with the oscillator and everything - it all works great, but I'd love to not have to take the chip out and put it back in the Arduino board everytime I want to change something.

Initially I thought I could just connect the TX/RX pins of the Arduino to the pins on the Atmega chip itself and just hit my in-circuit Reset button in sync with Upload, but no dice.

Is there another connection I have to make for this to work?


Thanks,
Drew
7  Forum 2005-2010 (read only) / Troubleshooting / Re: issue with digital pins? on: January 08, 2010, 10:39:26 am
Solved!  I was getting some random values due to the way I had wired it.  Also was using a bad switch.


Thanks!
8  Forum 2005-2010 (read only) / Troubleshooting / Re: issue with digital pins? on: January 08, 2010, 01:45:25 am


That's the schematic I used.

What's strange is that it works fine for pins 6-12.  Pins 1-5 and 13 all read HIGH regardless if anything's hooked up or not.  That's what leads me to believe something is wrong.
9  Forum 2005-2010 (read only) / Troubleshooting / issue with digital pins? on: January 07, 2010, 10:37:03 pm
Hello all,

I'm new to Arduino and microcontrollers in general.
I'm building a MIDI control board, and I need to implement a lot of switches.
Before I start using multiplexers/shift registers, I wanted to try setting up a single switch with the Arduino.

I used a pull-up resistor and connected a switch to one of the digital pins, but the serial print showed that the first 5 were stuck in HIGH state.  I reset the board, set them to Input, etc., but they still register HIGH regardless of what I do.


Does my board have a short in it?

Thanks,
Drew
10  Forum 2005-2010 (read only) / Interfacing / Program not startin on external power input? on: January 23, 2011, 06:50:43 pm
Hey guys.

Basically, I'm running the Arduino board off of a 12V power supply, receiving MIDI and turning lights on and off.  The midi adapter is connected to RX.  The circuit works perfectly when the Arduino is powered off USB, but nothing happens when it's powered by the 12V adapter.

I thought I read that this was due to RX have a floating value, so I put a 10K resistor between RX and ground - this made no difference.

Thanks,
Drew
11  Forum 2005-2010 (read only) / Interfacing / Re: creating large LED sign on: January 18, 2011, 02:14:31 pm
Bump for help on this.

Can anyone help me calculate the base resistor voltage for a transistor with collecter current ~400mA?

edit:datasheet:

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00001984.pdf
12  Forum 2005-2010 (read only) / Interfacing / Re: creating large LED sign on: January 14, 2011, 10:56:27 am
Okay perfect.

Well, math tells me that the average current by the entire array will be 400 mA (4 LEDs in each string, 20 strings).

By the way, I'm in Victoria, Canada.  I'll update the profile, heh.

Thanks.
13  Forum 2005-2010 (read only) / Interfacing / Re: creating large LED sign on: January 13, 2011, 11:39:49 pm
Cool, thanks.  I got a 12V 1000mA adapter and am using sets of (4 LEDs with a 68 Ohm resistor in series) in parallel.  This works great, but the only transistor I could get without doing another Digikey order is a TIP29c.  I know that it's NPN and that it'll handle 1000mA at the collector but I'm not sure what the gain is.  How might I figure out what resistors to use?
14  Forum 2005-2010 (read only) / Interfacing / Re: creating large LED sign on: January 12, 2011, 09:30:48 pm
Thanks for the replies.  They're all white LEDs, voltage drop across each is 2.7V, average drain 20 mA.  I'm going to go with a 12V supplt and follow that calculator posted.  Fantastic.

TIP102 or TIP120?  Any reason for those in particular?

I guess the transistor would have to be able to handle 600-1000 mA of current running through it.
15  Forum 2005-2010 (read only) / Interfacing / Re: creating large LED sign on: January 12, 2011, 01:41:14 pm
Also, 2A is a lot to be running through cardboard, yes?
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