Your motor shield is probably dropping a few volts. Since you don't need
to reverse the current in a solenoid simply use a MOSFET to switch it (don't
forget the free-wheeling diode across the solenoid terminals). You'll then
get all 12V across the solenoid.
That solenoid is rated for 50 seconds maximum (then you have to wait minutes
for it to cool down again I suspect). The specifications do not quote a duty-cycle
alas, which would be useful information.
The fact is I would avoid using "traditionnal" assembly because I heard that MOSFET are really delicate and I don't want them to break before or in the middle of my gig... This is why I try to do that with my Motor Shield (and because it's a little bit easier).
But if there is no alternative I'll reconsider that.
About what you said on cycles and cool down, it really worries me. Do you mean I'll not be able to use them for this idea of some sort of "acoustic drum machine" I have ? It's a really bad news for me...
I thinked that the "50sec" part indicated that I couldn't send pulses of more than 50 seconds.
And I don't have more informations about these solenoïds.
The fact is I would avoid using "traditionnal" assembly because I heard that MOSFET are really delicate
Not the case. MOSFETs are reliable, and great for such an application as driving a solenoid.
As Mark said, most motor shields will drop about 2 volts, so if you provide 12volts, you only get about 10volts (so weaker solenoid). What voltage are you providing the motor shield now?
If you do decide to use the motor shield, you only need one control pin, not two. Let us know if you want details.
The fact is I would avoid using "traditionnal" assembly because I heard that MOSFET are really delicate and I don't want them to break before or in the middle of my gig... This is why I try to do that with my Motor Shield (and because it's a little bit easier).
But if there is no alternative I'll reconsider that.
About what you said on cycles and cool down, it really worries me. Do you mean I'll not be able to use them for this idea of some sort of "acoustic drum machine" I have ? It's a really bad news for me...
I thinked that the "50sec" part indicated that I couldn't send pulses of more than 50 seconds.
And I don't have more informations about these solenoïds.
What you point me here poses me a big problem...
There's nothing inherently delicate about a MOSFET, but like all components you
do have to use them within their ratings. In particular with MOSFETs you have to
drive the gate properly and not let the gate-source voltage exceed the maximum.
It sounds like you need continuous duty solenoids? Or something with at least a duty-cycle
rating given for various current levels. There are ways to reduce the continuous current
in a solenoid without compromising the initial current on switch-on (resistor and capacitor),
which might solve your problems with the heat?
MarkT:
There's nothing inherently delicate about a MOSFET
What someone had told me is that they're very sensitive to static electricity and that I can "blow" them just by manipulating.
But I believe you if you tell me otherwise.
Ok, I undestand better now, thanks. My power supply provide 12v max... So I think that in any case I'll be forced to use a MOSFET assembly.
I don't think so, unfortunately, because of this 2v drop thing. But, just to know, you mean one wire of my solenoïd connected on "B"'s positive outlet and the other one directly connected to the negative wire of my power supply ?
MarkT:
There's nothing inherently delicate about a MOSFET, but like all components you
do have to use them within their ratings. In particular with MOSFETs you have to
drive the gate properly and not let the gate-source voltage exceed the maximum.
Do you think I could use TIP120 for example? I've seen that they're rather "universal"...
MarkT:
It sounds like you need continuous duty solenoids? Or something with at least a duty-cycle
rating given for various current levels. There are ways to reduce the continuous current
in a solenoid without compromising the initial current on switch-on (resistor and capacitor),
which might solve your problems with the heat?
Well... I don't know if I understand you correctly... Sorry (I'm still trying to improve my english and my Arduinish, but it's far from perfect as you can see).
But, for what I understood, no, for the moment I don't need different "strike forces", velocity. I just want simple impact for example on percussive instrument. So the movement must be strong and fast, but quite repetitive (to create a sort of rythme).
For resistor and/or capacitor for reduce heating, do you mean with the Motor Shield ? Between it and the solenoïd ?
Am I understandable ? And am I answering your post ?
But, just to know, you mean one wire of my solenoïd connected on "B"'s positive outlet and the other one directly connected to the negative wire of my power supply ?
No. I was referring to the connections to drive the motor shield. For each channel, there are 3 inputs. Two will control the direction of the motor (and/or stop it). The third is the enable. If you don't need two directions, you should just strap the two direction controls opposite (one to ground, the other to +5volts). Then you send a signal from an output pin of the arduino, to the enable input (such as ENA).
What is the resistance of the solenoid? The datasheet doesn't say. It says the maximum continuous power dissipation is 1.1W. If the 12V nominal coil voltage is the maximum continuous voltage, then that implies a resistance of about 130 ohms and current draw of just under 100mA. If that is the case, then you don't need a power mosfet; an NPN transistor such as BC337 will suffice.
So I suggest you measure the resistance of the solenoid and let us know what you find.
Ok, so if I get it, you said me I have to go through orange and white plugs in the center of the shield ? That's it ? Because what I did until now is that:
I'm doing it wrong, right ?
dc42:
What is the resistance of the solenoid? The datasheet doesn't say. It says the maximum continuous power dissipation is 1.1W. If the 12V nominal coil voltage is the maximum continuous voltage, then that implies a resistance of about 130 ohms and current draw of just under 100mA. If that is the case, then you don't need a power mosfet; an NPN transistor such as BC337 will suffice.
So I suggest you measure the resistance of the solenoid and let us know what you find.
Sorry for this late reply but my tester was malfunctioning so I had to go buy another one today.
Your estimate was perfect, the resistance of the solenoïd is 130 ohms.
When I bought my new multimeter I took the opportunity to take two BC337 so I will try.
Is it good if I do something like that with it ?:
dc42:
Yes, that's correct, except you need to decrease the resistor to about 330 or 470 ohms.
It works fine and it's not overheating anymore !
Last question: I've got some BC547-C and BC557-C in stock. Can I use them instead of BC337 with my other solenoïds ?
Well... Holding 50ms seems to be good for a prompt and effective impact. But I don't know how often I will ask solenoïds to strike. It depends of "rhythm" I want... But 3 times a second seems to be a fairly substancial number already.
Do you think it wouldn't work correctly or overheat if it have to hit more often or longer ?
Cynips:
Last question: I've got some BC547-C and BC557-C in stock. Can I use them instead of BC337 with my other solenoïds ?
BC557 is PNP so not suitable for this circuit. BC547 is just about OK, however you would be running it at its absolute maximum continuous collector current rating (100mA). So I suggest you buy more BC337.
dc42:
BC557 is PNP so not suitable for this circuit. BC547 is just about OK, however you would be running it at its absolute maximum continuous collector current rating (100mA). So I suggest you buy more BC337.
The fact is I would avoid using "traditionnal" assembly because I heard that MOSFET are really delicate and I don't want them to break before or in the middle of my gig... This is why I try to do that with my Motor Shield (and because it's a little bit easier).
Motor shield is probably designed to drive a motor, not a solenoid. The requirements are somewhat different. Motor is normally going to operate using PWM, solenoid is going to require plain DC current. And watch the time limitation, on your solenoid.
The armature of a solenoid is going to be moved in one direction by a magnetic force, and in the other direction by a spring. The characteristics of these two movements are going to be somewhat different. If you are going to try something like hitting a drum with the solenoid, you need to think about that physical process.
michinyon:
Motor shield is probably designed to drive a motor, not a solenoid. The requirements are somewhat different. Motor is normally going to operate using PWM, solenoid is going to require plain DC current. And watch the time limitation, on your solenoid.
In the Motor Shield overview they said we can drive solenoids with it.
I knew solenoids can't use PWM, but I thought that I can drive them after reading this technical sheet.
michinyon:
The armature of a solenoid is going to be moved in one direction by a magnetic force, and in the other direction by a spring. The characteristics of these two movements are going to be somewhat different. If you are going to try something like hitting a drum with the solenoid, you need to think about that physical process.
I also know how this type of motor works, physically.
I do some test at the moment and it seems rather conclusive for my purpose. I'll see if it lasts...
