LED Driver 0-10v Dimming

[Arzeo]

I was looking at an LED driver today which has a dimming function built into. This driver can use 0-10v dimming and resistance dimming. I really can't find any information on how these dimming functions actually work inside the driver. Looking through the datasheet there is information/graphs about the 0-10v dimming, but nothing about resistive dimming. Through a thread I read online, I found that resistive dimming is supported by this driver. I just have one question I cannot wrap my head around.

This driver's output is at a maximum when the purple/grey wires are open but is at a minimum when 0v is supplied to the wires. How does this work, isn't 0v being supplied the same as having an open circuit?

Here is the link to the driver's datasheet https://hubbellcdn.com/specsheet/LED-75W.pdf The dimming function information can be found on page 3.

[atmfjstc]

Having 0V at the end of the wires means they are shorted, not open circuit. It even says so in the datasheet:

0-10V dimmable version output will be 100% with Purple/Gray open and minimum with Purple/Gray Shorted.

[GerryR]

"0" volts generally means "tied to ground."  Think of it as a potentiometer with one side tied to 10 V and the other tied to 0 V, as the wiper of the pot moves toward the 0 V terminal.  (0 V is not necessarily "ground" although it can be; terminology again!)

[Arzeo]

I mentioned that in my post, the purple/gray wires have to be connected to some variable output 0-10v supply though. If your supply is not providing any voltage how is it shorted?

[Arzeo]

"0" volts generally means "tied to ground."  Think of it as a potentiometer with one side tied to 10 V and the other tied to 0 V, as the wiper of the pot moves toward the 0 V terminal.  (0 V is not necessarily "ground" although it can be; terminology again!)

This is what is confusing me, you can use a potentiometer as a dimmer for this driver. Where at 0 ohms it is a shorted and at high ohms essentially open. I am more confused about the 0-10v dimming aspect because that requires an input of 0-10v on the wires. If you can just use a potentiometer as a dimmer on the input wires then there has to be some output voltage(on the "input" wires) right? If so, how can you have 0-10v of input on wires that are already providing an output? Maybe I am just confusing myself or there is something which is flying right past me.

[Zero999]

"0" volts generally means "tied to ground."  Think of it as a potentiometer with one side tied to 10 V and the other tied to 0 V, as the wiper of the pot moves toward the 0 V terminal.  (0 V is not necessarily "ground" although it can be; terminology again!)

This is what is confusing me, you can use a potentiometer as a dimmer for this driver. Where at 0 ohms it is a shorted and at high ohms essentially open. I am more confused about the 0-10v dimming aspect because that requires an input of 0-10v on the wires. If you can just use a potentiometer as a dimmer on the input wires then there has to be some output voltage(on the "input" wires) right? If so, how can you have 0-10v of input on wires that are already providing an output? Maybe I am just confusing myself or there is something which is flying right past me.

The dim input has 2mA constant current source connected to it, with an open circuit voltage of around 10V. The LED brightness depends on the average voltage on the dim input.

The dim input can be controlled by a voltage, resistance and quite often PWM, since it's the average voltage, which determines the brightness. If a low impedance voltage source, capable of 2mA is connected to the dim input, the brightness will simply change, with the applied voltage.

Ohm's law states the voltage is proportional to the resistance, so connecting a 500R potentiometer to it, will give a voltage range of near zero to 0.002*500 = 10V.

This is very common feature with LED drivers.

[Arzeo]

Ohm's law states the voltage is proportional to the resistance, so connecting a 500R potentiometer to it, will give a voltage range of near zero to 0.2*500 = 10V.

Thanks for the reply, this seems fairly close but had one more thing to say.

While the 500ohm example makes sense, a lot of brands seem to need much higher resistances such as mean well drivers which use 100k ohm potentiometers for dimming. This specific driver apparently needs ~40k according to the manufacturer and a couple users claim to use around ~20k. I found this forum where a couple users were testing resistance dimming on this driver https://ledgardener.com/forum/viewtopic.php?f=15&t=747.

I would want to connect 3-5 of these for parallel dimming, and it seems as you connect more it would be harder to dial in the dimming because of the logarithmic curve of it. Because of this, I feel like 0-10v dimming would be much more convenient(and linear), but most 0-10v dimmers are built into light switches. Do you know of an easy way I can make a 0-10 dimmer with parts such as a 10v power supply, I just can't find much information online?
Could I just use a 10v ac converter with a 500 ohm potentiometer wired in series on the positive output connected to the dimming input?

[tunk]

It's probably made to be compatible with this old system:
https://en.wikipedia.org/wiki/0-10_V_lighting_control

[Zero999]

Ohm's law states the voltage is proportional to the resistance, so connecting a 500R potentiometer to it, will give a voltage range of near zero to 0.2*500 = 10V.

Thanks for the reply, this seems fairly close but had one more thing to say.

While the 500ohm example makes sense, a lot of brands seem to need much higher resistances such as mean well drivers which use 100k ohm potentiometers for dimming. This specific driver apparently needs ~40k according to the manufacturer and a couple users claim to use around ~20k. I found this forum where a couple users were testing resistance dimming on this driver https://ledgardener.com/forum/viewtopic.php?f=15&t=747.

I would want to connect 3-5 of these for parallel dimming, and it seems as you connect more it would be harder to dial in the dimming because of the logarithmic curve of it. Because of this, I feel like 0-10v dimming would be much more convenient(and linear), but most 0-10v dimmers are built into light switches. Do you know of an easy way I can make a 0-10 dimmer with parts such as a 10v power supply, I just can't find much information online?
Could I just use a 10v ac converter with a potentiometer wired in series on the positive output connected to the dimming input?

I got the decimal point wrong. Post edited. It's also possible there's an error in the data sheet and the current is much lower.

All you need is a small 0V to 10V power supply.  If you're happy with it only going down to 1.24V, rather than zero, the TLVH431 can be used to make a 1.24V to 10V supply, which can be powered from the LED driver's constant current source.
http://www.ti.com/lit/ds/symlink/tlvh431a.pdf

[Jwillis]

I believe the 0-10V dimmers are triac controlled. Just slapping in a potentiometer  will likely result in a greater light show than the LEDs your powering.

[Zero999]

Well this is an LED dimmer, so it won't be TRIAC controlled and I hope that anything requiring a 0 to 10V signal would have appropriate isolation and won't smoke if connected to a potentiometer, TRIAC controlled or not.

Here's a simple circuit using the LM358 as a buffer the TL431 voltage reference. Note only one op-amp in the package is actually used. The other is configured as a unity gain stage, with the input connected to 0V. The pin-outs for the LM431 and LM358 can be found on the data sheets.

http://www.ti.com/lit/ds/symlink/lm158-n.pdf
http://www.ti.com/lit/ds/symlink/tl431.pdf?

[Zero999]

If you just want an off the shelf solution, then I've had another look. They generally don't go down to 0V, but 1V will probably be good enough.

https://www.tlc-direct.co.uk/Products/VLMFP1M.html?source=adwords&ad_position=&ad_id=415703895087&placement=&kw=&network=u&matchtype=&ad_type=&product_id=VLMFP1M&product_partition_id=304858067660&campaign=shopping_switches_sockets&version=finalurl_v3&gclid=EAIaIQobChMIwcqGy-WU6AIVFODtCh1ULQYjEAQYAiABEgLq1fD_BwE
https://www.cometlighting.co.uk/ep1-dimmer-1-10v-max-10w-white.html?gclid=EAIaIQobChMIwcqGy-WU6AIVFODtCh1ULQYjEAQYBCABEgK-tPD_BwE
https://uk.rs-online.com/web/p/lighting-controllers/3011918/

[Arzeo]

Yeah, 1v would be fine. These drivers arent really supposed to dim below ~5% because it causes stress on the driver and can decrease lifetime i guess.

[Psi]

Just something to be aware of with LED drivers.

Some of them are very slow to start, like 2 seconds from power to light.
This is sometimes fine and sometimes really annoying. 

If you have one powered from the main light switch for room lighting is really weird when you flip the switch and nothing happens immediately.