The main goal of this project is to design a DC motor controller, We had a DC motor controller that its control circuit has been damaged. Here we are attempting to design a new control circuit for the controller. But before we can design the control circuit, we needed to know the power circuit design. To improve our design and make the most suitable control circuit.
SN74LS04 NOT GATE.
Step 1: Checking the Old Controller Power Circuit and Draw It.
The next step is to draw the diagram of the power circuit. And i did that many times and this is the final one.
Step 2: Building the First Circuit to Control the Duty Cycle to Control the Mosfet.
Step 3: Connecting the Arduino Circuit on Test Board and Try It on the Controller.
The Arduino couldn’t sent high voltage pulses and after checking the old control unit we saw an optocoupler connected with a mosfet driver in order to send pulses. the output voltage of the old control unit was around 12v. so we need to modify our control circuit to make it suitable.
Step 4: Draw the Old Control Unit Circuit Diagram.
this circuit couldn’t be done because we didnt find the needed components
Step 5: Building a Control Circuit With Arduino Using an Optocoupler
The circuit in the previous step couldn’t be done because we couldn’t find the needed components.
In this step we tried a different circuit to test the power circuit of the controller. we used an optocoupler with the Arduino to control 12v instead of the 5v from the Arduino pin. you can see the output waveform on the right. we also added 2 not gates on the output of the optocoupler to have fully squared waveform.
The motor worked using this circuit, but we couldn’t change the value of the output from the power circuit.
Step 6: Trying to Use the Old Control Unit Components.
Step 7: Using an Op-amp to Amplify the PWM From 5v to 15 V Maximum.
We used a non-inverting op-amp circuit to amplify the Arduino signal. From the picture above you can see formulas that we needed.
The gain of the op-amp is set using this formula:
a = Vout/Vin = 1+Rf/R2 which give us the following,
a= 1+ 10k/4.7k = 3.1 .
And the Vout= a*v(in).
since we are using the PWM the value of the input in the op-amp is not fixed, it will goes form 0-5 v thus,
when the input of the op-amp is 1v the output will be a*v(in) = 1*3.1 = 3.1v
and when the input of the op-amp is 5v the output will be a*v(in) = 5*3.1 = 15.4v .
Read more: DC Motor Control Unit for an Old Controller.