On Wed, Aug 7, 2013 at 12:05 AM, Epic Jefferson <jeffreyconcepc...@gmail.com > wrote:
> Hey Charles, > > it seems like this might work. i got some pnp transistors and built the > circuit from julianvogels site. > The only problem is that the LED on the test circuit barely lit up. I > think it's because the transistors are not for 20mA, none were available. > i'll check another electronics store to see if i find some. > I think you just need smaller resistors. Every transistor in a 3-pin package I've ever seen could run 20mA or much greater. Swapping the transistors will have no effect on the amount of current. Chuck > >> There are two ways to solve your problem: >> >> The proper one is to use PNP transistors or P-channel mosfets (remember >> I already told you about that ? :)) >> >> See this document, you can find the wiring at the end: >> >> http://julianvogels.de/wp-content/uploads/2013/06/stromkreis_transistorschaltung_final-1024x627.png >> >> >> http://julianvogels.de/extending-pwm-output-pins-with-a-texas-instruments-tlc5940-led-driver/ >> >> >> The good enough one is to put a pull-up resistor (10k works) on every >> NPN transistor base, and use the TLC as a pull down. In this case, the >> on-time on the TLC corresponds to the off-time on the solenoid. Also >> when the arduino reboots and every time the BLANK is issued, every >> solenoid will act for a veeeeery short time. This can be a big problem >> in your project. I did this for a 96 channels motor+led strip system, >> and I regret not using PNPs instead. >> >> >> Enjoy, >> >> -- >> Charles >> >> >> >> Epic Jefferson wrote: >> > Hey guys, >> > >> > updating on this project. I got the pwm shields and i've hit a wall. The >> > driver circuit I'm using to control the solenoids via arduino is this >> one >> > from instructables >> > (link< >> http://www.instructables.com/id/Controlling-solenoids-with-arduino/)>) >> > and >> > it uses a single pin to control the pwm signal. >> > >> > The pwm shield (link< >> http://www.practicalmaker.com/products/arduino-shields/pwm-shield-assembled >> >) >> > is >> > based on the tlc5940 which requires each pin to have it's own ground >> > instead of a common ground across all drivers. This is a problem because >> > all of the information i've found suggest that the signal from the pin >> > controls the gate (transistor - TIP102). But i think, in the case of the >> > tlc5940, the 5v supply is constant and the ground is being controlled, >> > that's why it works perfectly for LED's but seems to be ill suited for >> this >> > circuit. >> > >> > Any suggestions on how to modify the instructables circuit for use with >> the >> > shields? or would the circuit have to completely change? >> >> _______________________________________________ >> Pd-list@iem.at mailing list >> UNSUBSCRIBE and account-management -> >> http://lists.puredata.info/listinfo/pd-list >> > > > > -- > www.epicjefferson.com > www.avmachinists.org Puerto Rico based Art Collective/ Non-Profit Org > > _______________________________________________ > Pd-list@iem.at mailing list > UNSUBSCRIBE and account-management -> > http://lists.puredata.info/listinfo/pd-list > >
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