Solenoid actuator pushing and pulling with constant current

Hello guys,

It has been a while since I started studying about motors, actuators, solenoids and PWM power control with Arduino. My plan is to use Arduino to control the force frequency of a solenoid actuator, allowing a sweep from forces from 1 Hz to 200 Hz. Not sure if that will possible, though, I am still experimenting/studying.

Anyway, I bought a solenoid actuator from China (AliExpress) and decided to test it today. I just plugged it into a DC adapter I bought specifically for this (with appropriate voltage and current ratings).

But I got surprised when the solenoid keeps pushing and pulling while connected to the power. I thought that should only happen with the power was shut down or something like this, as this is what I did some time ago while dealing with solenoid water valves (they only close/open when power is off/on).

I already measured the voltage from the DC adapter, and it is stable at 12V.

What am I missing here guys? Is there any chance this solenoid has some feature which makes it turn on and off? I tried to look for specs using the model number, but it was unnsuccesful.

Best regards.

Additional info:

Youtube video of the testing: Solenoid testing Solenoid specs: Voltage: 12VDC, Current: 2.5A, Stroke: 10mm, Force: 55N DC adapter specs: INPUT: 100-240V~ 50-60Hz Max.0.8A / OUTPUT: 12V 2.5A Similar solenoids I bought, but different specs (original seller does not exist anymore): AliExpress, Amazon

My guess is that power supply is going into OCP (over current protection) mode , and 1 second later trying to restore power - again unsuccessfully. Try beefier power supply.

What is the coil resistance of that solenoid?

Hello guys, thanks for the tips and great insights! Did not though about it.

Indeed, just measured the coil resistance now and got 2.5 ohms. With 12V, that gives a current of 4.8 A, much more than the power source can handle.

So, should I buy another power source or do you think I could any a resistor or something like that?

Also, since the post is already here, I will ask for some guidance regarding this project: would you think it is feasible to make a solenoid respond fast enough to have it actuating at 300Hz? It would be only stroking a maximum of 1mm, and with a force of less than 1N.

I am trying to get my head around the physics of the problem but I am having a hard time evaluating whether what I want is doable with an Arduino, transistor and custom made coil, or would it require advanced tools.

Did they send you a 6V version? Interesting, aliexpr link shows a picture 12V 500 mA. You can lower a voltage, to prevent a damage to a solenoid. Plz., read a note at amazon: "Please pay attention:As an actuating element of an automation equipment ,because the current is large, the single cycle can not be electrified for a long time.The best operate time is in 2 seconds.If the operate time is too long,the electromagnet temperature will rise.T"

My understanding, its design for short time operation, in pulse mode, open a door or something, and with long recovery timing .

I'm in doubt it could have response time for 300 Hz - 3 msec, you better to try a high power speaker instead of electromagnet.

Indeed, perhaps they sent me a 6V version instead of 12V.

Regarding the response time, would have any reference about how could I calculate the response time of a solenoid?

ren1: Indeed, perhaps they sent me a 6V version instead of 12V.

Regarding the response time, would have any reference about how could I calculate the response time of a solenoid?

It all depends! The return spring, the mass of the armature, the inertia of the moving armature, the shape of the current pulse. Many variables. And each soldenoid will be different.

Paul

The physical arrangement of the magnetic circuit will also have a strong influence on the acceleration profile of the armature. You can design one for more force at the start of travel (faster) or more at the end (greater pushing power).

Basically if you know all the dimensions, material properties, its possible to simulate the behaviour and get an estimate of the response time.

Or just read the datasheet ;)

You'll be lucky to get any response greater than say 10Hz from a slugged solenoid (ie solid metal armature) like the one you illustrated. Apart from electrical 'inertia' due to armature inductance you also have to overcome mechanical inertia due to armature mass. You will find that at lower frequencies you require less drive voltage to achieve the required motion whilst at higher frequencies you will need higher voltage (more 'kick') to achieve similar motion. The arduino cannot output a variable (analogue) voltage so you will also require some means of converting the PWM output into a variable analogue 'power' driver.

Thinking about this again, 200Hz is in the domain of voice-coil motors, not solenoids.

MarkT: Thinking about this again, 200Hz is in the domain of voice-coil motors, not solenoids.

Which are usually 'iron-less' to reduce both mass and inductance

Thanks a lot for the inputs guys!

MarkT: Basically if you know all the dimensions, material properties, its possible to simulate the behaviour and get an estimate of the response time.

I have found some papers that present design equations relating magnetic field force with solenoids parameters, such as number of could, wire diameter, current, length, etc. But all on the electrostatic domain. In electrodynamics, I am still looking for equations that allow me to evaluate response time.

jackrae: You'll be lucky to get any response greater than say 10Hz from a slugged solenoid (ie solid metal armature) like the one you illustrated. Apart from electrical 'inertia' due to armature inductance you also have to overcome mechanical inertia due to armature mass. You will find that at lower frequencies you require less drive voltage to achieve the required motion whilst at higher frequencies you will need higher voltage (more 'kick') to achieve similar motion. The arduino cannot output a variable (analogue) voltage so you will also require some means of converting the PWM output into a variable analogue 'power' driver.

I can't recall the exact frequencies I was able to get from that solenoid, but from the top of my head it seem to agree with what you said (around 10Hz or a lot bit higher). Frequencies greater than that only caused the solenoid to hum and either stay permanently "open" or "closed", with not enough power to move the plunger. Important to remember that solenoid has a stroke of 1 cm, which is very high. I need way less than that, around 0.1 mm or even less.

I think I did not provide enough context for my application (even though it diverges from the original intention of the post): I want to create an excitation device that could apply small periodic/harmonic forces for experimental structural dynamics. Small forces such as 0.1 N would suffice. But I have to be able to control the excitation frequency, which will start at 1Hz and go up to 200Hz.

So basically it would excitate (bump the plunger, or push and pull a part of a body) with many different frequencies.

I will look more at voice coils, I do not know them very well. Are they actually speakers? If yes, I don't know if the sound waves will be able to apply the excitation level (in terms of force) I need to excitate the experimental bodies.

Might I suggest a change of concept. Use a servo motor to provide the rotational speed of 1RPS (60RPM) to 200RPS (12000RPM) You might have to provide gearing to get the upper speed limit As an alternative to a servo, you could use a simple DC motor and feedback its running speed to the controller to achieve constant speed. Connect the servo/motor output shaft to a crank bearing eccentric driving a linear coupling rod That's the basics of an electric toothbrush.

jackrae: Might I suggest a change of concept. Use a servo motor to provide the rotational speed of 1RPS (60RPM) to 200RPS (12000RPM) You might have to provide gearing to get the upper speed limit As an alternative to a servo, you could use a simple DC motor and feedback its running speed to the controller to achieve constant speed. Connect the servo/motor output shaft to a crank bearing eccentric driving a linear coupling rod That's the basics of an electric toothbrush.

That seems to be a way more appropriate concept! I will definitely explore it! Thanks a lot jackrae!

ren1: I will look more at voice coils, I do not know them very well. Are they actually speakers?

I said "voice-coil motors", you have but to google this.

MarkT: I said "voice-coil motors", you have but to google this.

hah, I skipped the "motors" part, that's where I got lost. Thanks and sorry :)