Designing a variable current circuit

In summary, the speaker has a system linked to a car that uses an electrolysis unit to run at 5A. They are currently using a Ring Smartcom Towing relay to control the unit, but it requires tuning for each vehicle and is time consuming. They want to add a unit that will allow them to use a single concentration of electrolyte and adjust the current with a potentiometer, but they have found that potentiometers can only handle 1W of power. They have found a diagram for a switching power supply, but are unsure about the power requirements and whether the LM117 is necessary. They are seeking help from qualified individuals to solve this problem.
  • #1
Gizmokev
1
0
Ok here is my problem

I have a system which is linked into a car. The system is an electrolysis unit designed to run at 5A. The system is wired in as per the 1st attached diagram.

So positive and negative are taken from the battery and placed into a Ring Smartcom Towing relay (PN RCT460). This simply stops the unit from working unless the alternator is running (engine on). I can replace this by simply finding an ignition live wire and tapping into that. The live is then fed into the electrolysis unit where it does its thing.

My problem I need resolving is that I have to tune each unit to the vehicle it is being installed on and this is currently done by changing the electrolyte strength to either allow more or less amps. This is a tricky and time consuming process.

I want to fit a simple unit into the system that will allow me to have a single concentration of electrolyte and throttle back the current being sent to the unit so that I can fine tune the system by simply adjusting a screw or similar.

Initially I thought a simple potentiometer would suffice until I read that they won't handle much more than 1W of power. At full power the system is using 69W at 13.8V (assumed alternator output).

So I have done some searching and found diagram 2 which will hopefully work but it aint cheap to build and I am wondering if it is a little over engineered for what I need to do. I am also not sure of the power requirements on the resistors in the diagram and the possibility of removing LM117 as this is the most expensive part and possibly does not need to be there going off other diagrams I have found. http://www.national.com/mpf/LM/LM338.html#Overview" [Broken]. Also what do the capacitors do in this diagram?

So are there any clever people out there that can help me in my quest to solve this apparently simple problem (in my head anyway although I am not anyway a qualified EE).

Over to you guys and gals
 

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  • #2
You need a switching power supply. Its not going to be an easy thing to do.
 
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1. What is a variable current circuit and how does it work?

A variable current circuit is a circuit that allows the user to control the amount of current flowing through the circuit. It typically consists of a variable resistor or potentiometer that can adjust the resistance and therefore the current in the circuit. By changing the resistance, the amount of current can be increased or decreased as desired.

2. What are the components needed to design a variable current circuit?

The main components needed to design a variable current circuit include a power source, a variable resistor or potentiometer, and a load. Other components such as wires, switches, and LEDs may also be necessary depending on the specific circuit design and purpose.

3. How do you calculate the current in a variable current circuit?

The current in a variable current circuit can be calculated using Ohm's Law: I = V/R, where I is the current in amperes (A), V is the voltage in volts (V), and R is the resistance in ohms (Ω). By adjusting the resistance with the variable resistor, the current can be varied accordingly.

4. What are some common applications of variable current circuits?

Variable current circuits are commonly used in electronic devices that require adjustable current, such as LED lights, motors, and audio amplifiers. They are also used in scientific experiments and research to control and measure electrical currents.

5. What are some safety precautions to keep in mind when designing a variable current circuit?

When designing a variable current circuit, it is important to be aware of the potential risks and take necessary precautions. This includes using appropriate voltage and current ratings for components, properly grounding the circuit, and using protective equipment such as gloves and goggles. It is also important to avoid touching any live wires or components while the circuit is powered on.

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