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I am using a Meanwell Led Driver LDD-1000H. It has a single pin for PWM input for dimming.

I have seen many sketches using the 555 to dim a LED but in these cases the LED was part of the circuit. How can I design a circuit based on the 555 to generate a PWM output on a single pin? (Additional question, I don't get how a signal is passed on with a single pin..).

If I want to vary the frequency of the PWMoutput, can I just replace R2 with am adjustable resistor or do I need the two diods as drawn below?

Thanks in advance for your reply..


Thanks very much for your answer. That would be essentially the following circuit:

pwm with 555

Is there a way to get cheaper component as the current and voltage are much lower than those used when the motor is driven like here:

http://www.dprg.org/tutorials/2005-11a/index.html

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    \$\begingroup\$ It's a little unclear what you're asking. The LDD-1000H requires a PWM input. One possible way to make that PWM signal is to use a 555. So you'd assemble a 555 circuit to produce the PWM signal and connect the output pin of the 555 to the input pin of the LDD-1000H. \$\endgroup\$ – Dan Laks Oct 13 '14 at 7:02
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The LDD-1000H needs an externally generated PWM signal. It doesn't care much where the signal comes from, as long as its within the specifications of the datasheet. A 555 timer is one way to generate that PWM signal.

Think of the circuit as two parts separate parts that connect together.

PART 1: The 555 timer to generate a PWM signal. I'm just using a generic astable configuration. Use whatever 555 circuit you plan to use.

schematic

simulate this circuit – Schematic created using CircuitLab

PART 2: The LDD-1000H that accepts a PWM signal and gives current to the LEDs.

schematic

simulate this circuit

Assemble these two circuits and connect the two nodes marked "PWM SIGNAL FROM 555" together. The 555 timer provides the PWM signal and the LDD-1000H translates that PWM signal into current for the LEDs.

Note that the voltage supply for the 555 timer does not have to be the same as the supply for the LDD-1000H. You can use different supplies as long as the ground references between the two supplies are connected. Also notice that the LDD-1000H requires a PWM signal between 2.5V and 6V. Therefore, the 555 timer must be supplied with a voltage in that range. Not all 555 timers can operate as low as 2.5V, so make sure you pay attention to the operating range of all parts you use.

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