Meanwell LDD PWM questions.

Thread Starter

AJS14

Joined Feb 4, 2014
10
Hello,

http://www.meanwell.com/mw_search/ldd-h/LDD-H-SPEC.PDF
The Meanwell LDD series datasheet says this about remote on/off and PWM dimming:

DIM: ~-Vin>2.5~6VDC or open circuit
PWM Frequency: 100~1KHz

Does this mean that there should be 2.5-6v coming back out of the device to the power supply? When it says open circuit it's not talking about the -Vin wire being open but the PWM wire right?

PWM frequency means that any PWM signal in this band of 100-1Khz will work to drive the PWM? The duty cycle % being carried somewhere on that frequency band.



Thanks in advance.
 

ronv

Joined Nov 12, 2008
3,770
Hello,

http://www.meanwell.com/mw_search/ldd-h/LDD-H-SPEC.PDF
The Meanwell LDD series datasheet says this about remote on/off and PWM dimming:

DIM: ~-Vin>2.5~6VDC or open circuit
PWM Frequency: 100~1KHz

Does this mean that there should be 2.5-6v coming back out of the device to the power supply?
No, it means the pwm signal should be above 2.5 volts.
When it says open circuit it's not talking about the -Vin wire being open but the PWM wire right?
Yes the pwm wire

PWM frequency means that any PWM signal in this band of 100-1Khz will work to drive the PWM? The duty cycle % being carried somewhere on that frequency band.
Yes



Thanks in advance.
 

Thread Starter

AJS14

Joined Feb 4, 2014
10
http://forum.allaboutcircuits.com/threads/leds-555s-flashers-and-light-chasers.19075/#post-117641

So this input frequency seems a bit on the low end.
Im looking at using Bill's 5.3 figure on his 555 page and using .47uF as the capacitor and a 1K5 for R2 and a 10K pot in R1.
There's a comment I found that current on r1 needs to be under 10mA so If I were planning on using a TLC555 running the network on 5v R2 would have ~3.2mA going across it.

Using these resistor values with that size timing cap gets me just within the boundaries of the PWM spec on the LDD.

Also fig 5.3 shows a pull up resistor in a block with a red LED and transistor. If I don't intend to drive that LED and I just want to send the PWM signal out to the LDD can I just use the pull up resistor and leave the rest out?
 

ronv

Joined Nov 12, 2008
3,770
I would just use the one on the left without the LEDs.

Then you can just drive it with pin 3. The 555 has an active pull up.
 

Thread Starter

AJS14

Joined Feb 4, 2014
10
Are there specific diodes I should use for CR1 &CR2?

The equation here goes way up to 14kHz at low values of R1. Since the values sum I can add whatever value I need in series with R1 to cap the frequency for the spec on the driver right?

thanks again.
 
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