Non dimming driver for Cree LMH2 8000LM?

CoveAxe

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But it looks like the drivers available need a 10VDC source in order to work.

That doesn't make any sense. These modules have a forward voltage of ~46V. It's very unusual to have a driver increase the DC voltage. Could you post what drivers you were looking at?
 

arek98

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If you want to dim it though even to just set level lower than max you can add potentiometer. Connect one pin to ground wire and middle pin to sense wire (actually it does not matter which one goes where), third pin of pot disconnected.
It creates a voltage divider with resistor that is in PSU connected to sense wire.
I don't know what is an internal resistor value but I guess it would be something about 10kOhms or slightly bigger. Assuming 10kOhm, external pot should be about 100kOhm (logarithmic should be fine). You can try this safely. If you pick to big you will not be able to dim until close to a range of pot and then it will dim quickly with little turn. If you pick to small it will be dim on max (i.e., max with pot connected will be lower than PSU max output).
 
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SemiMan

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Could be anywhere from a 10k to 250k (or more/less) pot for proper operation. Unfortunately the Cree data sheet is just slightly better than useless so no way to predict.

The spec on 0-10 source current is quite wide.
 

arek98

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It would be bad of Cree if pot would need to be 10KOhm, it would mean that internal resistor is just 1kOhm, 10mA current flowing from sense wire to ground when set to minimum dimming (wires connected directly or pot turned all the way down). I think they would like to keep it around 1mA top but you never know.

If OP is up to it he can find exact value of internal resistor.
Get 100kOhm pot and multimeter.
Measure voltage of sense wire when disconnected (multimeter between sense wire and ground wire of dimmer input). It should be ~11V
Torn pot somewhere to the middle, measure its resistance between lets call it left pin and middle one. Adjust pot to about 25kOhm (you can use resistor with similar value, I would use 20-50kOhm).
Connect the same pins to dimmer input.
Measure voltage across them.

Now you have Rp (resistance of pot), Vi (input voltage to divider measured in step 1 when sense wire is disconnected and current is not flowing thru internal resistor), and Vp (voltage across pot).
From this internal resistor value Ri is Rp/(Vi/Vp-1)

Once you know Ri best pot would be one with 10 times bigger resistance or little more (assuming open sense pin has 11V, if it is closer to 10V then dimming pot needs to be x times bigger that difference between open pin voltage is bigger than 10V, e.g., if open pin voltage is 10.5V then pot needs to be 20 times bigger resistance then internal resistor), logarithmic preferably (because one part of divider is constant and linear will not change Vp quickly enough to see difference).
 

SemiMan

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I see what you are trying to communicate but your assumptions are not accurate.

Open circuit voltage on 0-10 can be anywhere from a bit over 10v to 15v. The spec is 15v but I have seen higher.

As well, you are assuming a voltage source and pull up and that may not be the case. It would be something that approximates a current source or current limited power source.

Technically you can source up to 2ma but most circuits are more in the the 10s to 100s of UA.

1ma and 10k = 10v. Your 10ma extrapolation is wrong.

Semiman
 
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