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.
[image: Inline image 1]
On Mon, Aug 5, 2013 at 6:42 AM, Charles Goyard cg@fsck.fr wrote:
Hi,
You're not doomed !
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_transistorschal...
http://julianvogels.de/extending-pwm-output-pins-with-a-texas-instruments-tl...
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/)%3E)
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?
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