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“Solenoid test” by dargs01, using our solenoids!
Small push-pull solenoid. Solenoids are basically electromagnets: they are made of a big coil of copper wire with an armature (a slug of metal) in the middle. When the coil is energized, the slug is pulled into the center of the coil. This makes the solenoid able to pull (from one end) or push (from the other)
This solenoid in particular is fairly small, with a 30mm long body and a ‘captive’ armature with a return spring. This means that when activated with up to 24VDC, the solenoid moves and then the voltage is removed it springs back to the original position, which is quite handy. Many lower cost solenoids are only push type or only pull type and may not have a captive armature (it’ll fall out!) or don’t have a return spring. This one even has nice mounting tabs, its a great all-purpose solenoid.
To drive a solenoid you will a power transistor and a diode, check this diagram for how to wire it to an Arduino or other microcontroller. You will need a fairly good power supply to drive a solenoid, as a lot of current will rush into the solenoid to charge up the electro-magnet, about 100mA, so don’t try to power it with a 9V battery!
FEED
Fred Astaire – eat your heart out!
Comment by Stephen Upham — January 30, 2012 @ 10:08 am
The schematic shows a 1000 to 2200 ohm resistor in the base lead to the Arduino. Since the Atmega processor can drive up to 20 ma, and the base/emitter voltage on most Si transistors is .6 to .7 volts the voltage across that resistor will be about 4.4 volts (assuming the Arduino running at VCC=5v) so to limit the output current we can drop that resistor value to as low as about 220 ohm. The beta (current gain) of a typical power transistor will be about 100 (it can be much more in the case of a power Darlington or less in the case of some VERY high power transistors) so with 20ma base current we can drive up to 2A of current at the collector with the transistor in saturation. Note that the above is a “rule of thumb” good for a ‘ballpark’ figure, you’ll need to look at the actual transistor data sheet to nail it. With a 1000 ohm resistor we are actually looking at about 500ma saturated collector current for a “typical garden variety transistor”.
Comment by K Scharf — January 30, 2012 @ 10:37 am
OK, so I see 12 solenoids, and that translates in my mind as the chromatic scale (or all of the notes in 1 octave on a piano). Without the 12 glasses of water, bells, or chimes, can you name that tune?
Comment by Jeremy Saglimbeni — January 30, 2012 @ 12:44 pm
I’ve since got the midi working.. http://www.youtube.com/watch?v=xLntRgCNzsw uses Timothy Twillman’s MIDI library https://github.com/tymmothy which rocks!
Comment by dargs — January 31, 2012 @ 2:59 am
@ dargs – Nice!
Comment by Jeremy Saglimbeni — January 31, 2012 @ 7:53 pm