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

[Charles Z Henry]

On Wed, Aug 7, 2013 at 12:05 AM, Epic Jefferson <jeffreyconcepcion at 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?
>>
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>
>
>
> --
> www.epicjefferson.com
> www.avmachinists.org Puerto Rico based Art Collective/ Non-Profit Org
>
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