12v .5Amp Fan with resistor on 2.1Amp ciruit?

[DJM0007]

Can you install a 12V fan that pulls .5amps on a 2.1amp circuit with a ~1.5ohm resistor installed before the fan?
Assume you have plenty of voltage left in your circuit.

 

[Abiqua]

yeah in theory but since voltage wont be constant without other measures you could have problems with undervolting...fan doesnt come on if voltage doesnt reach a certain threshold... or overvolting....fan goes kablooey with too much voltage....

 

[DJM0007]

What keeps the COBs from going Kablooey if too much voltage when using a constant current driver?

 

[Abiqua]

What keeps the COBs from going Kablooey if too much voltage when using a constant current driver?

a couple different things.....but yeah it can happen and you can google thermal runway for this effect....

the problem is using current in a diode not voltage....and it gets deeper than that without breaking down more

thnik of the possibilities like this......so we have series and parallel wiring and CC and CV on top which all have different characteristics

 

[DJM0007]

I will research the thermal runway effect

I do understand the basics of voltage and amperage and parallel/series and CC CV, but those characteristics are what get me

So for an example:
If you have 3x Vero29 Gen 7 Type B (1.8A @ 52V) wired in series on a HLG-320H-C1750 driver
This would pull 156V from the COBs and the driver is capable of 183V

What will happen with this extra voltage? Applied to the COBs or just ignored?

I understand it is ignored because the COBs are only pulling 156V at the max current of this dirver.
No possible way for these COBs to take this extra voltage (driver amperage output max already)

But you could add in something more (extra cobs/fans) and utilize this leftover 27Volts? correct?

It is a good idea of get within a certain % of the rated load for that driver I would imigine.
So in this case within 10% (assume) of the 320W = 290W minimum.

I very well could be thinking about this wrong

 

[Abiqua]

I will research the thermal runway effect

I do understand the basics of voltage and amperage and parallel/series and CC CV, but those characteristics are what get me

So for an example:
If you have 3x Vero29 Gen 7 Type B (1.8A @ 52V) wired in series on a HLG-320H-C1750 driver
This would pull 156V from the COBs and the driver is capable of 183V

What will happen with this extra voltage? Applied to the COBs or just ignored?

I understand it is ignored because the COBs are only pulling 156V at the max current of this dirver.
No possible way for these COBs to take this extra voltage (driver amperage output max already)

But you could add in something more (extra cobs/fans) and utilize this leftover 27Volts? correct?

It is a good idea of get within a certain % of the rated load for that driver I would imigine.
So in this case within 10% (assume) of the 320W = 290W minimum.

I very well could be thinking about this wrong

you are right for the most part...a diode using CC aka cob and driver will draw varing amounts of voltage against a set amperage....so that 27 volts does exist but it could be more like 25v on startup, 28v's on warmup etc...and fans use Constant voltage .....as in ....they can vary their current up to the Max current so thats fine...What plays out will be a small clusterfuck.....fans dont have a wide range of voltage tolerance especially above max rating...usually only 14-15v`s for a 12v for example...so its this balancing act because the driver is CC and not a CV like most wall warts for instanc3e...you have to get above the minimum threshold voltage to get the fan to spin, but also keep it below the max rating...so really to answer your questin, what you proposed could work for the "high" side but don;t forget about your minimum threshold as well, imho a big pain in the ass unless you understand the circuit real well....it gets tricky is all

computr crashed...using tablet sorry for hooked on fonics spelling....

 

[DJM0007]

I am following you now. Atleast 95% haha
Thanks ALot!

So next question,
If I wired in 3x 9V .1A fans (with 1.7Kohm resistor) in series along with the 3x 52V 1.8A Vero29 Gen 7 wired in series, all together. Using the single HLG-320H-C1750 Driver
This circuit would pull 183V @ 1750mA give you 320.25W

Is anything wrong with this? It seems I could fill my driver up completely with this setup.

 

[SPLFreak808]

For a few reasons you would probably want to run the fan off its own power supply.

Running an led driver that hard will lessen its efficiency.

Adding a resistor to a driver line is a waste of power further reducing driver efficiency.

If your fan internally shorts in a series configuration its possible to damage anything sensitive on the same line with a slow constant current driver.

 

[DJM0007]

This is what I was expecting to hear! Thanks!

 

[CobKits]

Running an led driver that hard will lessen its efficiency.

running drivers hard increases their efficiency

 

[SPLFreak808]

running drivers hard increases their efficiency

i set myself up lol, I forget all about 240vac drivers thats mybad.

there are plenty of different drivers and power supply configurations it would depend on the driver used and how you use it.

For example, running the above posters driver (hlg320) on 110vdc will slowly drop efficiency once you go past 70% load however it should gain efficiency if he's using 240vdc.

 

[CobKits]

For example, running the above posters driver (hlg320) on 110vdc will slowly drop efficiency once you go past 70% load however it should gain efficiency if he's using 240vdc.

actually its as efficient at 90 and 100% as it it is at 70, and ever so slightly more efficient at 80%

 

[SPLFreak808]

actually its as efficient at 90 and 100% as it it is at 70, and ever so slightly more efficient at 80%

Do they have a spec sheet i can look at or something? Sounds really odd that a 110 pwm supply won't slightly drop off when driven at 100 compared to 70 lol.