Simple Led PWM driver

thatoneguy

Joined Feb 19, 2009
6,349
What will the 3rd wire be? If it is for power, it's not much use unless you run a 4th wire for ground.

What will the maximum distance from the transmitter to the furthest receiver be?

The protocol linked above isn't designed for the distances you are looking at. It is targeted more towards inter-board communication in a small system.
 

Thread Starter

LostInSpace

Joined Mar 16, 2010
24
What will the 3rd wire be? If it is for power, it's not much use unless you run a 4th wire for ground.

What will the maximum distance from the transmitter to the furthest receiver be?

The protocol linked above isn't designed for the distances you are looking at. It is targeted more towards inter-board communication in a small system.
the small LOAD slave vil kun use 2 wire
the big LOAD slave vil-use 3 wire

my house is on a plot 40 * 40 meter och master module will be located in the middle,

maximum distance will be 30-40m

I've done some testing with normal eth cables of 100 meters using 1200 Hz at a viewing off twisting wire and it seen ok.
 
I've done some testing with normal eth cables of 100 meters using 1200 Hz at a viewing off twisting wire and it seen ok.
That's an impressive distance! It would be interesting to know the results when a loaded bus of leds (480ma = 30ma x 16 ) enters the picture, and what guage of wire is going to supply that load?

Have just glossed over kranenborg doc. The protocol's net result seems similar in function to a Dallas one-wire. Dallas has the parasitic mode (two wire, gnd and data) whereby a master controlled pullup transistor is enabled to charge the one-wire (slave) sensor cap during writes and reads from the scratchpad.

After browsing the RS485 stuff online, that seems like a worthwhile project. A PIC with an EUSART with slave address interrupt mode, and two twisted pair seems to simplify things.
 

Thread Starter

LostInSpace

Joined Mar 16, 2010
24
I finish with the Simple PWM Led Drive

The Picaxe 08M can make PWM to 1Mhz for 1 to 99% pwm

with very simple command

pwmout 2(pin), (div into 1mhz), 4 * x%

At pwmout 10Khz , 10% pwm Look like this

PWMOUT 2, 100, 40 ( it continue until change)

5% PWM give a ok light(8 in serie )
25% PWM give Full light (29 mA current on the LED)

total 5 part + x nr off LED
 

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SgtWookie

Joined Jul 17, 2007
22,201
Your LTSpice schematic is using a voltage symbol for B1.
It should instead be a capacitor.

You do not show a current sensing resistor below the LED "string", so your PICAXE will have no way of sensing the average LED current.
 

Thread Starter

LostInSpace

Joined Mar 16, 2010
24
Your LTSpice schematic is using a voltage symbol for B1.
It should instead be a capacitor.

You do not show a current sensing resistor below the LED "string", so your PICAXE will have no way of sensing the average LED current.

I only use this Spice to show my end circuit

B1 is a 100uf 63v cap

In my test board i have a 1ohm resistor in series with the LED's and find 29mA at 25% pwm on curcuit supply at 5V

in the end construction i have remove the 1ohm resistor

and end with 2 step light 10% and 23% PWM from the PICAXE

I'm happy with the final construction of the light driver

which should be simple

I ended up with 8 LED's was just as test finally driver module will have 2 to 6 LED's
 

SgtWookie

Joined Jul 17, 2007
22,201
OK, but if you test with just 2 LEDs in series instead of 8 LEDs in series, you will find that they will get too much current.
 
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