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Topic: Will this work? MOSFET PWM strips controller. (Read 298 times) previous topic - next topic

dgameiro

Hello.
Will these schematic work to control 2 separate meters of led strips? (Led strip Rgb Ip65 7.2w/m).
Tell me if im wrong and why, in what im going to type.

-Resistance between the Arduino and the gate will limit the current, its not really needed since its a mosfet and the current will be low, but wont hurt right (220 ohm?).

- I have to look for a logic level mosfet, that is full on with 5V, and that can handle the current it will be asked for. (Each led takes about 20ma full white, so 20ma * 30leds = 600ma  for each colour, so i get one that can handle 1,5A).

- If i want to get 4 strips, i simply use a shift register 74hc595 to get more PWM outputs.

CrossRoads

Looks good. 220 limits current into the gate capacitance of the MOSFET, which can look like a short to +5  or Gnd as the signal changes: 5V/220 ohm = 22.7mA.

Low Rds, Logic Level N-channel MOSFET: A0I514 or AOI510.
http://www.digikey.com/product-search/en?keywords=aoi514
http://www.digikey.com/product-detail/en/AOI510/785-1487-1-ND/3603498
Power dissipated in the part = I^2 * R = .6A * .6A * .0119ohm (AOI514 with Vgs = 4.5V) = 4mW, nice & cool.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

dgameiro

Low Rds, Logic Level N-channel MOSFET: A0I514 or AOI510.
http://www.digikey.com/product-search/en?keywords=aoi514
http://www.digikey.com/product-detail/en/AOI510/785-1487-1-ND/3603498
Power dissipated in the part = I^2 * R = .6A * .6A * .0119ohm (AOI514 with Vgs = 4.5V) = 4mW, nice & cool.
My store doenst have that FET. Will this one do the job?

http://www.mixtronica.com/electronica-componentes-electronicos-semicondutores-transistores/3759-ap2306agn-hf-3tr-mosfet-n-30v-0-035-ohm-sot23-ap2306agn.html

And where do i put a potentiometer if i want to control the brightness? And for color mixing what can i do?

Thank you again

DVDdoug

Quote
- If i want to get 4 strips, i simply use a shift register 74hc595 to get more PWM outputs.
No.  PWM doesn't work through a shift register.   (At least not easily...)

Quote
And where do i put a potentiometer if i want to control the brightness? And for color mixing what can i do?
If you want to use pots, connect them to an analog input the same way as the Analog Read Serial Example.   Then, take that reading and convert it to a PWM value.    

If you want to directly adjust the red, blue, or green brightness based on the pot, you can use the map() function to convert the 0-1023 analog input to a 0-255 PWM value.

dgameiro

No.  PWM doesn't work through a shift register.   (At least not easily...)
Why? Ive seen some tuturials using shiftpwm arduino library. "ShiftPWM is a library for Arduino to control many PWM outputs using shift registers (for example 74HC595). "

And about the FET, will this one http://www.mixtronica.com/electronica-componentes-electronicos-semicondutores-transistores/3759-ap2306agn-hf-3tr-mosfet-n-30v-0-035-ohm-sot23-ap2306agn.html, do the same as A0I514?

Transistor Polarity: N Channel
Continuous Drain Current Id: 5A
Drain Source Voltage Vds: 30V
On Resistance Rds(on): 0.035ohm
Rds(on) Test Voltage Vgs: 4.5V
Threshold Voltage Vgs: 300mV
Power Dissipation Pd: 1.38W
Operating Temperature Min: -55??C
Operating Temperature Max: 150°C
Transistor Case Style: SOT-23
No. of Pins: 3
MSL: MSL 3 - 168 hours.

5A more than enought for what the colour channels ask for right? 4,5 Vgs and low Rds.



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