J
Joel Moore
Let me start by giving credit where due. I found this attractive LED
dimmer design on the following site:
http://www.e-f-w.com/community/modules.php?name=News&file=article&sid=10
I'm not at all familiar with MOSFETs (and to be honest my general
electronics skills are very limited...which is why I'm here) so I was a
little uncertain about how to proceed in adapting that design for 24VDC.
So I did some reading on MOSFETs and after getting even more confused
about them I simply changed the layout of the LED array to work with 24V
(6 LEDs and a 120 ohm current-limiting resistor in series) and plugged it
in. No problem despite the fact that the MOSFET gate is now seeing
nearly 24V rather than 12V. Then I connected 11 more of these LED
strings in parallel and ran that. Still no problems.
Here's where I'm a little uncertain. According to the article one IRF510
MOSFET should be able to handle up to around 16 LEDs before you have to
get something more powerful. But in my case I have 72 LEDs running
through a single IRF510. The chip doesn't even feel warm. Should I not
be surprised that I can support so many more LEDs simply by moving to a
24V design or is the author of that article either mistaken or being
overly cautious about his MOSFET?
Is there anyplace I can read a simple description of how to design with
MOSFETs? The back of the MOSFET package has a long list of parameters,
none of which mean anything to me. What's important to consider when
working with these things?
And can anyone see a possible flaw in this design? It almost seems too
simple to me. I don't want to implement this if it's likely to fail a
few months down the road. Commercial LED dimmers can cost hundreds of
dollars yet here we have a circuit for less than $10 (including a 555
timer which I'm not using in my case) which seems pretty effective to me.
So what's wrong with it?
Here's an ASCII version of my circuit:
24VDC -----------
| |
| |
10K LED ARRAY
| |
| |
| Drain
| |
-- Gate IRF510
| |
| Source
| |
470K |
| |
| |
-----------
|
Sinking
PWM
Output
|
GND---------
Thanks for any input on this.
Joel Moore
dimmer design on the following site:
http://www.e-f-w.com/community/modules.php?name=News&file=article&sid=10
I'm not at all familiar with MOSFETs (and to be honest my general
electronics skills are very limited...which is why I'm here) so I was a
little uncertain about how to proceed in adapting that design for 24VDC.
So I did some reading on MOSFETs and after getting even more confused
about them I simply changed the layout of the LED array to work with 24V
(6 LEDs and a 120 ohm current-limiting resistor in series) and plugged it
in. No problem despite the fact that the MOSFET gate is now seeing
nearly 24V rather than 12V. Then I connected 11 more of these LED
strings in parallel and ran that. Still no problems.
Here's where I'm a little uncertain. According to the article one IRF510
MOSFET should be able to handle up to around 16 LEDs before you have to
get something more powerful. But in my case I have 72 LEDs running
through a single IRF510. The chip doesn't even feel warm. Should I not
be surprised that I can support so many more LEDs simply by moving to a
24V design or is the author of that article either mistaken or being
overly cautious about his MOSFET?
Is there anyplace I can read a simple description of how to design with
MOSFETs? The back of the MOSFET package has a long list of parameters,
none of which mean anything to me. What's important to consider when
working with these things?
And can anyone see a possible flaw in this design? It almost seems too
simple to me. I don't want to implement this if it's likely to fail a
few months down the road. Commercial LED dimmers can cost hundreds of
dollars yet here we have a circuit for less than $10 (including a 555
timer which I'm not using in my case) which seems pretty effective to me.
So what's wrong with it?
Here's an ASCII version of my circuit:
24VDC -----------
| |
| |
10K LED ARRAY
| |
| |
| Drain
| |
-- Gate IRF510
| |
| Source
| |
470K |
| |
| |
-----------
|
Sinking
PWM
Output
|
GND---------
Thanks for any input on this.
Joel Moore