Go Down

Topic: Will this work? MOSFET PWM strips controller. (Read 69 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.



Go Up
 


Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

Arduino
via Egeo 16
Torino, 10131
Italy