[PD] electro-mechanical piano (player piano) - Arduino, Solenoid Issue

[Epic Jefferson]

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 at 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_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?
>
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-- 
www.epicjefferson.com
www.avmachinists.org Puerto Rico based Art Collective/ Non-Profit Org
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