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How hot should Rkcstr driver get?

I

IanBuckwell

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I am building a laser with an LPC815 diode and Rkcstr driver, it will be in a flashlight host but I wanted to test it and adjust the current first so I used a 9v battery I had handy, I set current to around 420mA with my dummy load.

When testing with dummy load and diode the driver seemed to get hot very quickly, how quickly do these drivers get hot and what is a safe maximum temperature?

When using these drivers in flashlight hosts do people use any kind of heatsink on the chip/driver to try and control the heat? thanks.
 





cust11

cust11

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IanBuckwell said:
I am building a laser with an LPC815 diode and Rkcstr driver, it will be in a flashlight host but I wanted to test it and adjust the current first so I used a 9v battery I had handy, I set current to around 420mA with my dummy load.

When testing with dummy load and diode the driver seemed to get hot very quickly, how quickly do these drivers get hot and what is a safe maximum temperature?

When using these drivers in flashlight hosts do people use any kind of heatsink on the chip/driver to try and control the heat? thanks.
Click to expand...


The rkcstr driver is a linear design and converts excess power into heat. It is not uncommon for these to get very very hot. The driver does not need to be heatsinked. SMD components are very tough! They go through ovens over 500F to reflow the solder.

-Mike
 
Gryphon

Gryphon

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Just a thought, if you used a battery setup with less volts, say 4AA's for 6V rather than 9V from a 9V batt, it MIGHT run cooler not having convert the extra juice into heat.

Just a thought thou :D
 
Flaminpyro

Flaminpyro

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15n6q1x.jpg
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you can epoxy a small finned alum heatsink to the chip to help with heat disapation. this one is big enough to be sawn in two for use on two regulator chips.
 
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E

ElektroFreak

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The 1117 regulator is rated to 150C. No matter how hot it feels, it's not that hot. 150C will burn you instantly.
 
N

nikokapo

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ElektroFreak said:
The 1117 regulator is rated to 150C. No matter how hot it feels, it's not that hot. 150C will burn you instantly.
Click to expand...

This.


The fact that components get hot doesn't mean they're burning. They can burn your skin because it can't take more than 50°C without getting burnt a little. BUT components can take a lot more than that, especially LM transistors, although most of them need a heatsink depending on the use you're gonna give them.


However it's okay if you wanna add a heatsink to the driver, it won't hurt ;)
 
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IanBuckwell

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I think the voltage when in my host will be less than 9v I used for testing as I will be using two 14500 batteires in series, which I believe are 3.6v or similar. So maybe it wont get hot quite so quick.

I think I will attempt to use a small heatsink if it will fit in the host as it wont do any harm. Thanks for the help.
 
HIMNL9

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I have a suggestion for you (that for me works with any type of drivers :D)

If you can get some silpads pieces, use them between your module and your host, they are isolant, so no short circuits, and transfer the most part of the heat on the host (and then dissipate it, ofcourse)

If you can't get them as samples from selling companies, as me, you can sometimes recover some of them from dismantled cd/dvd readers/burners ..... are these little pieces of "gum" that, sometimes (but unfortunately, not in all the models), you can find between the power IC's and the back plate of the unit (the first plate that you take away when you dismantle one)

can looks very differents, like these ones:

attachment.php


(pic very bad, today my webcam acts as drunk, sorry :p) ..... i always collect them, when i find them, cause i use them in some of my prototypes, time by time, and also for drivers heat dissipation.
 

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pwnstar

pwnstar

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Will the driver be more stable or energy efficient with a heat sink? A while ago I used thermal glue to put one on my 400mA driver.
 
HIMNL9

HIMNL9

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Well, overheating always interfer with correct functionality of electronic devices, so yes, cold is better :9

Also, considerate that the driver regulate the current dissipating the excess of power in heat (just for put it in a simple way ;)), and that usually they have an internal protection against overheating ..... so, keeping them more cold, make them work better, more efficent, and prevent power reductions or shutdowns from the internal protection circuits.
 
Mohrenberg

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it's completely normal for the rkcstr driver to get hot during use....
it's not abnormal for it to be hot enough as to be uncomfortable to the touch.
 
E

ElektroFreak

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HIMNL9 said:
Well, overheating always interfer with correct functionality of electronic devices, so yes, cold is better :9
Click to expand...


As long as it is below 150C (302F) it has not overheated and no cooling is necessary. 302F is REALLY FRICKIN' HOT. It will burn the crap out of you instantly. If your driver is not hot enough to burn the crap out of you instantly, then don't worry about it.
 
HIMNL9

HIMNL9

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Careful ..... looking on my datasheets, the maximum JUNCTION temperature for the 317 is 125C (150 is for the 117), and i re-state JUNCTION temperature, not case temperature ..... then you have to calculate thermal dissipation, thermal resistance junction/case and case/ambient and so on .....

Can say that, for safety, is better keep it not more than 80 / 85 C, if you want it live long and happy :D

(anyway, at 125C of junction temp, the thermal shutdown turn it off :p)
 
HIMNL9

HIMNL9

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Then, considering the design and (supposed) thermal dissipation, probably you can push it til 90/95C of body temperature, before the thermal protection circuit shut it off.

Anyway, 95C is a temp that don't let you keep it in your hand for more than 1 second (at least, if you're not a masochist :p :D) ..... think you can notice it, if it's becoming too hot :D

The only real problem, imho, is if you're using a driver inside an aixiz module, cause the heat from the driver adds to the heat from the LD, and all increase very quickly, and this is not too healty, for the LD (too bad that they don't have thermal protection circuits inside the can :p)

Uhm, wondering if, with the actual drivers IC's, that half of them have an external "enable" pin, is possible to build a thermal protection for the LD incorporated in the driver board, that still fit in a module ..... :)

BTW, LM117 and LM1117 are different, the 117 is 150C, the LDO 1117 is still 125C
 
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