Hi all,
I will start by saying I'm not very good with circuits yet. I'm fine with building something off a ready-made circuit diagram, even quite complex, but I must admit, I don't always understand what is each component for .
So, when the time comes to put something together myself, I have to ask for help. Here I am.
I am basically building a muscle wire actuator for a function in a model car of 1:87 size. Every millimeter of size is precious and large amounts of heat are not welcome and hardly possible. Long story short, I have a 3.6-4.2 volt power supply, depending on how happy the LiPo is in the car and I need to deliver constant current of ~50mA to the muscle wire. The resistance of the 2" section I will be using is around 24Ohm when "activated" (current flowing through).
The simplest solution would be resistor, but the size needed would not be small, the heat would be generous and it would not adjust to varying resistance of the muscle wire as it heats up/shrinks to provide the movement I need.
I have found some solutions on the net and this forum with transistors and ICs, but most of them are designed for Amps, rather than mAmps of current and start at 12V or so. The others diagrams require figuring out the values of the components yourself and I tried, but nope, not there yet .
The other thing that I maybe should ask about at the same time is that I need to switch this activator on and off from a "digital decoder". I am not sure how this matters, but I have heard people talking the fact the positive lead from the decoder is kind of common and switching leads for various functions are negative, I need to keep this in mind as not all traditional circuits can be connected that way (I was thinking optocoupler or something). If I just said something really strange, just ignore it, please . What would be the most space saving way of a switch?
Can anyone help with a complete circuit diagram? Must be a couple of components as far as I understand. Any data needed that I did not provide?
Thank you and BR,
/Edmunds in Riga, Latvia
I will start by saying I'm not very good with circuits yet. I'm fine with building something off a ready-made circuit diagram, even quite complex, but I must admit, I don't always understand what is each component for .
So, when the time comes to put something together myself, I have to ask for help. Here I am.
I am basically building a muscle wire actuator for a function in a model car of 1:87 size. Every millimeter of size is precious and large amounts of heat are not welcome and hardly possible. Long story short, I have a 3.6-4.2 volt power supply, depending on how happy the LiPo is in the car and I need to deliver constant current of ~50mA to the muscle wire. The resistance of the 2" section I will be using is around 24Ohm when "activated" (current flowing through).
The simplest solution would be resistor, but the size needed would not be small, the heat would be generous and it would not adjust to varying resistance of the muscle wire as it heats up/shrinks to provide the movement I need.
I have found some solutions on the net and this forum with transistors and ICs, but most of them are designed for Amps, rather than mAmps of current and start at 12V or so. The others diagrams require figuring out the values of the components yourself and I tried, but nope, not there yet .
The other thing that I maybe should ask about at the same time is that I need to switch this activator on and off from a "digital decoder". I am not sure how this matters, but I have heard people talking the fact the positive lead from the decoder is kind of common and switching leads for various functions are negative, I need to keep this in mind as not all traditional circuits can be connected that way (I was thinking optocoupler or something). If I just said something really strange, just ignore it, please . What would be the most space saving way of a switch?
Can anyone help with a complete circuit diagram? Must be a couple of components as far as I understand. Any data needed that I did not provide?
Thank you and BR,
/Edmunds in Riga, Latvia
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