Steve Anderson wrote:One thing I would like to give a 'heads-up' on... you need to make sure the 12V supply is truly 12V.
Considering an adjustable DC-DC converter for this job.
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Steve Anderson wrote:One thing I would like to give a 'heads-up' on... you need to make sure the 12V supply is truly 12V.
Klaas Robers wrote:Indeed, Steve is right. In some way you have to stabilize the light output of the LEDs. In the example of the current source, this source circuit is the stabilizer. In this case the "top" of the LED-chains can be connected to an unstabilized voltage that only has to be and stay "high enough".
But if you plan to run the LEDs PWM switched on a voltage with a rather low ohmic resistor in series, you need a stabilized voltage for it. Otherwise you will see all variations in the motor current also as brightness variations of your picture.
Measure the voltage of an adaptor. If a 12V DC adaptor gives an unloaded voltage of 12 volt, it will be stabilized. If the voltage is much higher, and only 12 volt when loaded with the indicated current, it isn't. Most heavy adapters are unstabilized, the lighter electronic adapters are stabilized. The heavy adpters contain a (heavy) transformer. That is old fashioned technology.
There is another way to see that a power adapter is stabilized. If the input voltage is defined as 100-240V AC, it is definately stabilized.
Andrew Davie wrote:The difference being that the voltage changes don't affect the current nearly as much.
Andrew Davie wrote:Considering an adjustable DC-DC converter for this job.
Steve Anderson wrote:Andrew Davie wrote:Considering an adjustable DC-DC converter for this job.
The output is 5V, is that what you want in the context that we're talking about a 12V supply?
Klaas Robers wrote:It is not that bad that you drive the LEDs to 27 mA for peak white. Unless on a full whit field the software gamma correction will see that they only now and then run at this peak current. But if you can, check the temperature of the LED cluster when it runs. You placed the LEDs very close and heat can almost not escape. If you did not clip off the wires, these wires can act as a kind of heat sink. When LEDs get hot their light output (efficiency) drops (and they get even hotter). May be you can include a small fan.
Klaas Robers wrote:It is not that bad that you drive the LEDs to 27 mA for peak white. Unless on a full whit field the software gamma correction will see that they only now and then run at this peak current. But if you can, check the temperature of the LED cluster when it runs. You placed the LEDs very close and heat can almost not escape. If you did not clip off the wires, these wires can act as a kind of heat sink. When LEDs get hot their light output (efficiency) drops (and they get even hotter). May be you can include a small fan.
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