Decrypting LED ring Requirements

[4pyros]

Cliff, Are you trying to vary the brightness of the LEDS?
LED are not voltage controlled, they are current controlled.
YOU can use PWM to vary the brightness.
A 12 volt DC PWM motor controller like this would work fine.
**broken link removed**

 

[Cliff321]

Thanks. How does one go about establishing a maximum output.
When I hook these LED rings up to my little PSU I can set it to VDC at 7.5, 9, and 12 and at each increasing voltage the LEDS shine more brightly. The maximum is supposed to be 14VDC but my PSU doesn't got that high.
ERGO my conclusion that it is volts that control the brightness.

A PWM unit (if I am correct) imposes an on off cycle to the line current - - yes? The speed of the on/off determines the amount of energy reaching the load thus the brightness of the lamp, LED or motor speed. Faster cycles = brighter lights or faster motor speeds. Am I correct thus far?

What then would you say is the reason my LED rings illuminated differently at different voltages.
It bears noting that the retailer (when they had them for sale) claimed they ran at 9 - 14 VDC at 3 watts. The retailer said nothing about dimming them.

So While I understand the PWM statement, I don't get why I can dim or brighten them by changing voltages.

 

[ronsimpson]

Cliff, Are you trying to vary the brightness of the LEDS?
LED are not voltage controlled, they are current controlled.
YOU can use PWM to vary the brightness.
A 12 volt DC PWM motor controller like this would work fine.
**broken link removed**

The LED ring is not just LEDs. There are current limiting resistors. There fore it is working fine in voltage mode. It is fine to vary the voltage to change the brightness. Probably (almost no) current below 9 volts. Probably full current at 14 volts. (because of resistors)

 

[4pyros]

A PWM unit (if I am correct) imposes an on off cycle to the line current - - yes? The speed of the on/off determines the amount of energy reaching the load thus the brightness of the lamp, LED or motor speed. Faster cycles = brighter lights or faster motor speeds. Am I correct thus far?

Yes PWM runs full voltage duty cycles so the average power changes with duty cycle.

 

[4pyros]

What then would you say is the reason my LED rings illuminated differently at different voltages.
It bears noting that the retailer (when they had them for sale) claimed they ran at 9 - 14 VDC at 3 watts. The retailer said nothing about dimming them.

The current limiting resisters.

 

[Cliff321]

Here is a question:

I found this:
**broken link removed**
Which I can drive with a 24 VDC 4 amp psu.
But it has not got a way to limit the max voltage out put.

So can I just wire a pot inline with the out-put leads and use the pot on the board to establish a maximum volts and leave that one inside the enclosure (where fiddly little fingers can't mess with it) while placing the other final pot in a through the enclosure port to allow user adjustment?

Seems to me I could just replace the on board pot with one of those you need a screwdriver to adjust.

 

[4pyros]

So can I just wire a pot inline with the out-put leads

I dont think you can find one to handle the power the LEDs need cheaply.

If you make the current limiting resistors on the ring smaller you can get full brightness at 12 volts.

 

[Cliff321]

Swapping those resistors out would be a task way to fiddly for me.

 

[4pyros]

Swapping those resistors out would be a task way to fiddly for me.

Me too. But it can be done.