hi, in my project i have small sheet of special alloy that a wire of Ni-Cr is wind around it. by increasing the input voltage to wire, it will be warmer by internal resistance and the alloy will bend. i want to have flex sensor to sense the bending curvature and send it to Arduino to increase or decrease the output voltage to wire. the main source is 10v and 1A. can anybody help me please?
Hall Effect sensor maybe?
Flex sensor is indeed a problem with the heat.
Something to measure the distance one end of the bimetal (that's what you're using, right?) may be easier.
For the heating control, you don't normally control the voltage, it's much easier to control the current. Use a MOSFET and PWM to control it.
wvmarle:
Flex sensor is indeed a problem with the heat.Something to measure the distance one end of the bimetal (that's what you're using, right?) may be easier.
For the heating control, you don't normally control the voltage, it's much easier to control the current. Use a MOSFET and PWM to control it.
Flex sensor have a suitable distance from heating source and it's have very simple circuit, it mades by plastic and carbon, as it bends, the resistance in increased ( a role like Potentiometer resistance ) and after that, the current must be change. i need one map function to receive the resistance from sensor and map it to device(Wire) current input.
i don't know what is the MOSFET, is it work to my project? i want just to solve my project issue, the way is not so important, i am mechanical engineer and have little information about arduino. thanks for your attention.
I see one issue here. I think you want to make the metal bend to a certain extent, and keep it there. That calls for a bit more control, as you have to use the reading from the flex sensor to tell you where you are (it's a feedback), and have a setpoint (user input) that tells you where to go. Change the heat (PWM duty cycle) based on the difference.
You may benefit from PID control here. Can probably leave out the I for small, fast reacting heating wires.
Yaah, every things that you say is true and is my goal. now how i can do it? with arduino or any etc PID control? the flex sensor in flat mode have a about 50 k ohm resistance and in bended mode, 140 k. please tell me what part and circuit i need to control? these pics shows before and after heat and curvature.
A 100k series resistor should do fine for that sensor.
Hook it up, see what readings you get.
Wire up the heating wire with MOSFET switch, make sure you can control this properly.
Combine them together. The PID is the hard part.
For all the separate parts you'll be able to find lots of tutorials.
wvmarle:
A 100k series resistor should do fine for that sensor.Hook it up, see what readings you get.
Wire up the heating wire with MOSFET switch, make sure you can control this properly.
Combine them together. The PID is the hard part.
For all the separate parts you'll be able to find lots of tutorials.
OK. i buy one MOSFET IRFZ44N, Arduino UNO R3, I have sensor before. i write the pid controller, i define the pin 9 & 6 as PWM. as the sensor bends, the voltage in PWM pins is changed. i saw it by multi-meter. now please tell me where i must put the MOSFET? in the PWM pin, i can not have more than 5v. i need more about 10v, by mosfet.
Standard MOSFET circuit.
Output pin to the gate; pull-down resistor from gate to GND, load between positive supply and drain, source to GND.
Why two PWM pins? You have two heaters?
The voltage your multimeter indicates is an average. Connect it to a scope and you'll see the block wave.
Yaah, I have two heater. i bring every thing that you say to me, but i am week against you in electronic. can i ask you to draw me the circuit?
i buy one MOSFET IRFZ44N
You buy the wrong sort of FET, you need one like this:-
Grumpy_Mike:
You buy the wrong sort of FET, you need one like this:-
Tnx. Does it have a similar? i can not find it in stores.
Look for FETs with an L in the part number and then look at the data sheet at the Ron parameters, Resistance of the FET when on, and the conditions that is measured under is a 5V gate voltage.
These are called logic level FETs.
SMorteza:
Tnx. Does it have a similar? i can not find it in stores.
The IRLZ44N will do just fine, too. Note the L instead of the F.
And that Fritzing image misses the mandatory flyback diode - mandatory as it's a motor switch. Your heating element doesn't need this, so you can just replace the motor by the heating element and you'll be fine.
Grumpy_Mike:
You buy the wrong sort of FET, you need one like this:-
This product that you advise to me, is IRLB8721, and i can not find it, but i find the IRLB8743, does it works for me?
I also find and buy the IRLZ44N, that you say must have L in product type. thanks for your kindly guidance.
Yes that will be fine, the thing that tells you when you look up the data sheet ( just google the part number) is the bit that says:-
Very Low RDS(on) at 4.5V VGS
Which means the resistance between the drain and source ( Rds ) is low with only 4.5V applied to the gate.
Note that this will be even lower at higher gate voltages, you will see how much lower from the Rds(on) line in the static characteristics table.
SMorteza:
that you say must have L in product type
NO.
That's NOT a must, and also not a guarantee that it's a suitable type. That IRL/IRF thing is only for Infineon parts, other manufacturers have different naming. Other logic level FETs that I use a lot include the BSS138 and the PMV16UN - those work great at 3.3V levels, while the IRL types we're talking about here generally won't work at those lower voltages. They need >4V.
read the data sheet is the thing to do. That's conclusive, just a part number is a mere indication.
SMorteza:
This product that you advise to me, is IRLB8721, and i can not find it, but i find the IRLB8743, does it works for me?
Just look at the data sheet, at the very top it gives you the answer:
Very Low RDS(on) at 4.5V V GS
Looking further down it seems that this one may even work well at 3.3V gate levels. Interesting, as that's quite rare for MOSFETs in TO220 packages.
Looking further down it seems that this one may even work well at 3.3V gate levels.
Looked it up and Farnell ( Newark ) sell them at a pound a pop, so I might have to investigate them.
Thank you so much for your guides. actually i must look for low Rds at 4.5v??? this is data sheet of IRLZ44N and in it and in infeneon site, is written "low Rds(on)" and the type of it is T0-220AB. is it bad for my project yet? i must buy IRLB8743 that i found, instead of it?
This is for 44N
And this is for 8743
SMorteza:
Thank you so much for your guides. actually i must look for low Rds at 4.5v???
Around that voltage, indeed.
this is data sheet of IRLZ44N and in it and in infeneon site, is written "low Rds(on)" and the type of it is T0-220AB. is it bad for my project yet?
Page 2 of the IRLZ44N datasheet gives you the numbers for VGS=5.0V and even 4.0V. That 25-35mΩ on resistance should be good enough for your application.