In this article I describe how to make a 4-wire IAC valve tester with simple materials that you can have in your workshop or at home.
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As I had promised in my previous blog posts, I bring you a 4-wire IAC valve tester that you can do at home or mechanic shop without the need to purchase many materials.
If you want a tester that gives you better control of the IAC, I recommend this other tester that I made a complete 4-wire IAC Tester
Actually this tester is very common in the world of robot electronics, since for motors servomechanisms are used a lot stepper motors (which in effect is what the IAC is composed of) and well, to make rapid tests of torque without the need to build a controller circuit, we use this simple scheme that we will see below:
As you can see in the previous figure what we need is:
1.- An AC transformer that reduces the voltage of 110V that we have at home to 9V.
Well, although I have done tests with these valves and they manage to move very well up to 6V. The important thing is that the output voltage must be AC, it must not pass through any rectifier to convert it to DC.
2.- A pair of alligators.
To easily make connections without the need for splices.
3.- Four small terminals for the valve.
If you have the connector, then much better.
4.- Finally, a few centimeters of cables to make the fixed connections.
The circuit is quite simple and figure 1 speaks for itself, the most problematic is to identify the pins of the IAC valve to know what the coils are, but if you saw my article "How the 4-wire IAC works" it will be a piece of cake.
Important considerations when making this assembly:
If you do not know anything about electricity, I do not recommend that you ride the circuit.
As explained in my article "How the 4-wire IAC works" the step motor needs a pattern of positive and negative signals in the terminals so that the movement is achieved. This is where the alternating current comes in, where in one instant we have positive (+) on one cable and the other (-) at a rate of 60 times per second.
Now, to explain it as simple as possible without the use of equations or theorems ... when we place the coils in series and connect them to the alternate source of 9 VAC, we produce the pattern (+, -, +, -) and the (- , +, -, +) so we need two more to make it work. Then placing a capacitor in parallel with a coil or another we delay the flow of current (the capacitor is charged) by that coil during a cycle and we advance the passage of current (the capacitor is discharged) by that coil to the next cycle of the alternating current , in this way we produce (+, -, -, +) and (-, +, +, -).
The only problem with this system is that the steps that we have induced with the capacitor are very fast and therefore the torque of them is very low. This means that if the valve is too locked or static, back and forth movements will occur until the sequence of the field is properly coupled.
To try to mitigate this it is proposed to assemble the circuit shown below (figure 2) in order to energize the coils at will so that the field only operates when we need to operate the valve.
Mount the following circuit:
hat we need additional is:
1.- A push button normally open.
2.- A few centimeters of cables to make the fixed connections.
For IAC valves of the Magneti Marelli brand, which are those of the FIAT, below I show you the diagram:
The alligator must not be connected to the outputs of the transformer. You must go to the valve coil inputs. This ensures that only current is received when the button is activated. For the rest, it is the same as the circuit of Figure 1.
Here I show you a video where I assemble both circuits and the final recommendations.
Well, that's all for the moment, I hope you like it.
As an exercise, I propose to eliminate the caiman and place a three-way, two-step suiche. With this they would have an acceptable quality tester that they can use in their home or workshop.
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