well i did connect grounds....
and treshold voltage seems to be 2V and current 250uA....
Well im asking since maybe i dont know something that i should...well i am pretty sure that i do not know some things that i should in order to complete this project myself... but i hope that at the end of it i will have learned those things
If i understand correctly then there should be no problems with controlling 4 motors, since current that arduino can provide is 40mA and mosfet needs 250uA, but frequency will drop?
since current that arduino can provide is 40mA
That is the absolute maximum before damage starts. It is recommended, for long term safety, that you don't exceed 25mA.
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Threshold voltage is the voltage at which the mosfet starts to conduct, not the voltage at which it is fully on. To test the mosfet switching the motor, you need to apply at least 4.5v to the gate for typical logic level mosfets, and 10v for other types. So a 3v battery is likely to be insufficient.
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The mosfet does not take 250uA at the gate, that figure is the drain current at which the gate threshold voltage was measured. The gate of a mosfet looks like a capacitor. When the Arduino pin driving it changes state, the capacitor charges or discharges through the pin. The purpose of the series resistor is to limit the peak charge/discharge current to 40mA or less.
Hi again!
I dont know why...but this does not work...i use as a battery on scheme 9V and in place of arduino 9v battery as well but i tried it with arduino aswell. Battery that is battery on scheme heats up. Well i connect mosfet 1 pin is gate 2 is drain 3 is source as in datasheet. Basically like that http://circuits.datasheetdir.com/97/IRF520-pinout.jpg . I am really frustrated.... 3 days until the day that i have to hand my work over and the scheme does not work....
I made some photos of it if it will help u to help me please use it:D
http://oops.ee/wp-content/uploads/2012/05/DSCN3634.jpg
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That motor looks to me too big for a 9v battery to drive. I think the mosfet is turning on but the battery is unable to provide enough current to start the motor, so the battery is just getting hot. Also the connections made to the battery using sticky tape may not be connecting very well. To check that the mosfet isn't the problem, bypass the mosfet by connecting a jumper wire between the source and drain terminals.
Try using a battery pack made from 4 or more alkaline or lithium (or fully charged NiMh) AA cells to power the motor instead. Driving the mosfet gate from a 9v battery is OK.
well if i connect motor and battery directly, motor works.... Mybe mosfet applies some resistance?
About sticky tape... we doublechecked it and it outputs right voltage:SSS
In 3 hours ill be able to check everything again... i will write here again when the time comes
I just noticed from your photos that your 100 ohm resistor isn't properly connected. One end is correctly connected to the mosfet gate terminal, but the other end is plugged into the wrong row of the breadboard, so it isn't connected to anything.
Remember that mosfets are static sensitive devices, so don't touch that resistor until you are touching the source terminal of the mosfet (or something else connected to ground) with your other hand.
Yeah.. thx a lot
Sadly it didnt fix the problem...somehow no voltage is going to the drain(collector)
I can say this much that battery goes dry very fast....can it be that diode is dead? Or why else can batteries voltage drop in some minutes...
no diode is okay...i tried plus-diode-motor-minus..and motor does not work...i turn diode around and it works
FFTMaster:
Yeah.. thx a lot
Sadly it didnt fix the problem...somehow no voltage is going to the drain(collector)
The voltage on the drain should be very close to zero when the mosfet it turned on (i.e. +9v applied to the gate), and the same as the battery voltage when the mosfet is turned off (because the drain is connected to the +ve terminal of the battery through the motor).
FFTMaster:
no diode is okay...i tried plus-diode-motor-minus..and motor does not work...i turn diode around and it works
In your photo, the diode is the right way round (the diode in parallel with the motor, and the end with the stripe connected to the +ve terminal of the battery), unless you've acquired a diode that is incorrectly marked. If you turn the diode the other way round, it will bypass the motor and that will make the battery go flat very quickly.
dc42:
In your photo, the diode is the right way round (the diode in parallel with the motor, and the end with the stripe connected to the +ve terminal of the battery), unless you've acquired a diode that is incorrectly marked. If you turn the diode the other way round, it will bypass the motor and that will make the battery go flat very quickly.
I just thought maybe diode is dead, but no it is okay, i did test where i connected battery + to diode and at the other side of diode i placed motor and to the other side of motor minus of battery....this test showed that diode was okay, it allowed current to pass only in one direction.
About voltage being near zero at the drain when mosfet is working.... yes it is near zero... then i have to check wether current goes out of emitter somehow...maybe not enough for motor or something....
I just did some tests with mosfet..and it allowed current to go through when nothing was placed on the gate...
I also tested 2n2222 a bit and discovered that motor works when i take out resistor between battery and base, battery i used was 3v and even 100oom was too much...
omg....now it does not care what i put on the gate..it just works
Now it works with 5from arduino...the mosfet.... but it does not from pwm and digital output
Hi guys!
i have a lot of improvements... everything works...It seems problem was in the board...
First i will explain the situation and then i will tell u what i want to achieve...
Right now with the help of MOSFETs i supply motors. Its done by taking 220 V out of power supply and transforming it into 9V 3A. So now i need to supply arduino and motors separately...i want to supply arduino from same 9V. How can i do that... what parts do i need to do that...