<div dir="ltr"><div class="gmail_extra"><div class="gmail_quote">On Wed, Aug 7, 2013 at 12:05 AM, Epic Jefferson <span dir="ltr"><<a href="mailto:jeffreyconcepcion@gmail.com" target="_blank">jeffreyconcepcion@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hey Charles,<div><br></div><div>it seems like this might work. i got some pnp transistors and built the circuit from julianvogels site.</div>
<div>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.<br></div>
</div></blockquote><div><br></div><div>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.<br>
<br></div><div>Chuck<br></div><div><br> </div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div></div></div><div class="gmail_extra"><div><div class="h5">
<div class="gmail_quote"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
There are two ways to solve your problem:<br>
<br>
The proper one is to use PNP transistors or P-channel mosfets (remember<br>
I already told you about that ? :))<br>
<br>
See this document, you can find the wiring at the end:<br>
<a href="http://julianvogels.de/wp-content/uploads/2013/06/stromkreis_transistorschaltung_final-1024x627.png" target="_blank">http://julianvogels.de/wp-content/uploads/2013/06/stromkreis_transistorschaltung_final-1024x627.png</a><br>
<br>
<a href="http://julianvogels.de/extending-pwm-output-pins-with-a-texas-instruments-tlc5940-led-driver/" target="_blank">http://julianvogels.de/extending-pwm-output-pins-with-a-texas-instruments-tlc5940-led-driver/</a><br>
<br>
<br>
The good enough one is to put a pull-up resistor (10k works) on every<br>
NPN transistor base, and use the TLC as a pull down. In this case, the<br>
on-time on the TLC corresponds to the off-time on the solenoid. Also<br>
when the arduino reboots and every time the BLANK is issued, every<br>
solenoid will act for a veeeeery short time. This can be a big problem<br>
in your project. I did this for a 96 channels motor+led strip system,<br>
and I regret not using PNPs instead.<br>
<br>
<br>
Enjoy,<br>
<br>
--<br>
Charles<br>
<div><br>
<br>
<br>
Epic Jefferson wrote:<br>
> Hey guys,<br>
><br>
> updating on this project. I got the pwm shields and i've hit a wall. The<br>
> driver circuit I'm using to control the solenoids via arduino is this one<br>
> from instructables<br>
</div>> (link<<a href="http://www.instructables.com/id/Controlling-solenoids-with-arduino/" target="_blank">http://www.instructables.com/id/Controlling-solenoids-with-arduino/</a>)>)<br>
<div>> and<br>
> it uses a single pin to control the pwm signal.<br>
><br>
</div>> The pwm shield (link<<a href="http://www.practicalmaker.com/products/arduino-shields/pwm-shield-assembled" target="_blank">http://www.practicalmaker.com/products/arduino-shields/pwm-shield-assembled</a>>)<br>
<div>> is<br>
> based on the tlc5940 which requires each pin to have it's own ground<br>
> instead of a common ground across all drivers. This is a problem because<br>
> all of the information i've found suggest that the signal from the pin<br>
> controls the gate (transistor - TIP102). But i think, in the case of the<br>
> tlc5940, the 5v supply is constant and the ground is being controlled,<br>
> that's why it works perfectly for LED's but seems to be ill suited for this<br>
> circuit.<br>
><br>
> Any suggestions on how to modify the instructables circuit for use with the<br>
> shields? or would the circuit have to completely change?<br>
<br>
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</div></div></blockquote></div><br><br clear="all"><div><br></div></div></div><div class="im">-- <br><a href="http://www.epicjefferson.com" target="_blank">www.epicjefferson.com</a><br><a href="http://www.avmachinists.org" target="_blank">www.avmachinists.org</a> Puerto Rico based Art Collective/ Non-Profit Org
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