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Registered Member #3859
Joined: Sun May 01 2011, 03:47PM
Location:
Posts: 179
I am looking for a good TL494 - based circuit that can levitate an object that weighs 600 gramms, with a window of homeostasys of about 10mm and is driven by PWM. Hopefully a circuit that uses an optical feedback and not magnetic.
I have seen this circuit: and this
Maybe there is a cross between the two. I really like the idea of TL494 and I read a lot about this IC chip.
I don't want to deal with the Hall Sensor feedback because it is rather hard to adjust that window where I can hook my levitating load and it will neither fall, nor attach to the electromagnet core.
I am not confident enough in my electronics skills to develop that stage that feeds the analog signal to the TL494 from the phototransistors and the diode. I want to copy-cat the circuit somewhere.
Thank you. I am ordering electronic parts and this is why I am asking a lot of questions. I want to build a cheap torque balance that I can use in my experiments with physics and I want magnetic levitation to serve as the bearing.
Registered Member #3859
Joined: Sun May 01 2011, 03:47PM
Location:
Posts: 179
Would a circuit like this keep the MOSFET half-open? I want to work with big currents so I would rather build a circuit that either opens or closes the semiconductor.
Circuit from here may work: but I don't understand what I should feed into it. It is described with words how to build the stage
Any suggestions?
I am thinking about using several MOSFETs in parallel and employing rectified mains to drive a large electromagnet to get higher levitation capacity. Has anyone seen any PWM phototransistor ciruits? How can I modify the bottom circuit to use an optical feedback?
Was this ever build? I know it is has mistakes in it. I read that forum.
Registered Member #3859
Joined: Sun May 01 2011, 03:47PM
Location:
Posts: 179
I am planning on combining those two circuits because I don't want Hall Sensor in my project and I want PWM to drive the MOSFET.
So here is my circuit for driving PIN 1, the input of TL494.
How do I find out the input resistance or impendance of pin 1 of TL494? Is it equal to 12V divided by the input bias current of 0.2uA?
My simulation doesn't work for some reason I cannot explain. Node 9017 doesn't exist in my circuit. Can this circuit work with two 20mA phototransistors?
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Looking for a PWM (TL494-based) circuit for magnetic levitation that is simple and can support 0.6Kg
