Strength and size of linear actuator

I’m trying to find a ‘linear actuator’ that is capable of pushing a small 33g CO2 canister into a piercing valve, like nitrous oxide crackers. It needs to be a one off push to fully open the canister on the valve, stroke distance shouldnt need to be more than 10 mm. I will be running it through an UNO powered off a large mobile powerbank and is idealy wearable.
Is there anything smaller/cheaper than the pololu tranducers?

Hi Adam,
Sounds like a great project. When you say ‘transducer’, do you mean the Pololu linear actuators? Unfortunately, I don’t think we’d have anything off the shelf that could accomplish that besides those actuators, however, a motor with a high torque gearing to create linear motion could be an option.

How compact does this all need to be? If the answer is “not at all” then a central-locking actuator will perform beautifully. The stroke length is typically more than 10mm but if the push is only in one direction then you can probably leave dead-space. These can be purchased quite cheaply at any automotive electronics shop.

By choosing a high-torque servo motor and using an appropriate linkage, you have the freedom to trade off between linear force on the cylinder and stroke length. Now the neat thing here is that your servo is high-torque, you can just set the stroke to whatever you need and the servo will probably be able to deliver it.

The basic idea is that you have freedom over the length (L) of the push-rod, and the angle (theta) that the servo horn rotates. The smaller the angle, the greater the force (F) but this creates a shorter stroke (s).

I neglected to mention that you can also change the length of the servo-horn to the same effect.

Thank you both Sam and Michael,
The central locking actuator is a brilliant idea. It is exactly the action I have been looking for. I would like it to be smaller but i dont think that is going to happen, not for a prototype at least. Iv been looking at the slave door actuators (meant for a passenger seat rather than drivers seat master actuator). These have only two wires, so im guessing a positive or negative voltage would like control the direction of the actuator. Does that sound about right, and easy to control through an arduino?

Certainly does!
The actuators I’ve brushed with stroke in one direction when energised, and return to a neutral position when de-energised. Energising the actuator in one direction causes it to stroke eg. forward. Removing power often causes it to stroke back to centre. The converse is also true for reversing the polarity (stroke backwards, return)

You can easily experiment by connecting the actuator to a 12V supply and observing the behaviour.

You can get bidirectional control by treating the actuator as a simple DC motor and connecting it up to an H-bridge!
Note: I mean just driving it on/off in either direction. Don’t use any PWM code - that’s probably bad for the actuator.
If your actuator is the centre-returning variant, and you only need half the stroke length, then you could drive your actuator with a transistor (and a few other passives).

1 Like