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Review of electric circuit with Arduino

kitstudent

New Member
Hi guys!

I am currently working on a project for which I am in charge of the electronic circuit. However I have never worked with electronics before, therefore I am really desperate and unsure whether what I am doing is correct. If someone could help me out, that would be great! :)

So basically my goal is to heat and shape set the "sma wire" by Joule heating. For this I have to come up with a arduino controlled circuit that can heat the wire and depending on the temperature (measured by thermal camera) reached, I have to adapt the temperature again via adaptable voltage/current supply.

I hope I expressed myself clear enogh for someone to understand. I have attached my design for the circuit. Maybe someone could give me his/her opinion :))
 

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Diver300

Well-Known Member
Most Helpful Member
You seem to have the basics of a feedback control system, and that looks OK, but some details are missing.

The battery and the Arduino would need a ground connections.

The circuit diagram uses lines to represent wires, and also uses other lines to represent data connections that I would expect to be multiple wires. The form of the temperature measurement isn't clear. I assume the PC is a Personal Computer, and I don't know why there would be any need to have an A/D converter between a PC and an Arduino.

Depending on the form of the wire, how long and thin it is, the current needed to heat it up may be a lot. You need to make sure that the battery can deliver that current and the MOSFET is rated to take that current. It may be necessary to use some sort of transformer or buck regulator to create more current at a lower voltage, and that is another significant engineering challenge.

The basic idea, that the Arduino can read the temperature and then control the current via the MOSFET is fine. You might not need a gate driver if you use a logic-level MOSFET and you aren't switching the current on and off quickly.

If you are getting one of these working, it's important to make sure that each part of the control system works before letting it try to control on its own. You should make sure that the Arduino can read the temperature in conditions where nothing will be damaged if it doesn't, and also you should make sure that it can control the current with a load that won't be damaged if it is left on.
 

kitstudent

New Member
You seem to have the basics of a feedback control system, and that looks OK, but some details are missing.

The battery and the Arduino would need a ground connections.

The circuit diagram uses lines to represent wires, and also uses other lines to represent data connections that I would expect to be multiple wires. The form of the temperature measurement isn't clear. I assume the PC is a Personal Computer, and I don't know why there would be any need to have an A/D converter between a PC and an Arduino.

Depending on the form of the wire, how long and thin it is, the current needed to heat it up may be a lot. You need to make sure that the battery can deliver that current and the MOSFET is rated to take that current. It may be necessary to use some sort of transformer or buck regulator to create more current at a lower voltage, and that is another significant engineering challenge.

The basic idea, that the Arduino can read the temperature and then control the current via the MOSFET is fine. You might not need a gate driver if you use a logic-level MOSFET and you aren't switching the current on and off quickly.

If you are getting one of these working, it's important to make sure that each part of the control system works before letting it try to control on its own. You should make sure that the Arduino can read the temperature in conditions where nothing will be damaged if it doesn't, and also you should make sure that it can control the current with a load that won't be damaged if it is left on.
thanks for your input!
what exactly do you mean by "The battery and the Arduino would need a ground connections."?
Im sorry, I am really a beginner in electronics

I thought the A/D would be necessary to convert the temperature data into digital input for the arduino?

The idea is to switch the current rapidly and I thought the TVS, Capacitor are to to snub inductive spikes, which result from the large di/dt values during switching. So is it still valid to use a gate driver?
 

danadak

Active Member
Here is a non contact T sensor and code for Arduino.


If you use PWM (to control duty cycle, hence heat) to drive power MOSFET you do need a gate R and a driver for it.

Do you code in C ?


Regards, Dana.
 

kitstudent

New Member
Here is a non contact T sensor and code for Arduino.


If you use PWM (to control duty cycle, hence heat) to drive power MOSFET you do need a gate R and a driver for it.

Do you code in C ?


Regards, Dana.
thanks :) my teacher wants us to use a thermal camera tho

and yes c
 

rjenkinsgb

Well-Known Member
Most Helpful Member
what exactly do you mean by "The battery and the Arduino would need a ground connections."?
Im sorry, I am really a beginner in electronics
All sections, devices or modules etc. need both a power feed (usually positive) and return to 0V, the circuit "ground", which with a single supply such as the battery is battery negative.

You may also need a voltage regulator module to convert the 12V from the battery to 5V or 3.3V to run the Arduino, depending exactly what module or IC that is.
 

Diver300

Well-Known Member
Most Helpful Member
The idea is to switch the current rapidly and I thought the TVS, Capacitor are to to snub inductive spikes, which result from the large di/dt values during switching. So is it still valid to use a gate driver?
A gate driver is used if the control device can't produce enough current or voltage to switch the MOSFET strongly enough or fast enough.

The 5 V from an Arduino may be enough voltage, but it depends on the MOSFET.

A MOSFET has considerable gate capacitance. The output of an Arduino can only supply a limited current, so the MOSFET gate will take time to charge or discharge that gate capacitance and turn on the MOSFET. Turning on the MOSFET slowly will reduce the di/dt so reducing the problem caused by that, but it will mean that the MOSFET spends more time getting hot each time it turns on and off. If the control is slow, as with a thermostat where there are several second between each switching event, that isn't a problem, but if there is PWM or other fast switching, turning the MOSFET on and off slowly can make it generate a lot of heat.
 

Diver300

Well-Known Member
Most Helpful Member
I thought the A/D would be necessary to convert the temperature data into digital input for the arduino?
There has to be an A/D converter somewhere, but that would most likely be within the PC., or even the camera itself. It would be very unusual to connect a PC to an Arduino using an analogue connection.

I think that Arduinos have A/D converters within them anyhow.
 

sagor1

Active Member
Just use a PC serial port to communicate with the Arduino. That eliminates the A/D device. You just have to decide on what data/protocol you want to send from PC to the Arduino. Even simple text strings of a reading to the Arduino would do.
Or, feed the thermal camera data directly to the Arduino and skip the PC. You would have to know the data format from the camera.
 

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