Need help for building a 24v nicad battery charger

[Zabb Csaba]

Accidentally short circuited LED generates spikes in current and produces large reverse-voltage spikes, which destroys LEDs (wire self inductance).

Regards,

 

[chemelec]

I Don't have any of those Infrared LED's, But I do have some 1 watt and 10 Watt White LED's
Testing BOTH of these, the Heatsink on them is ISOLATED from Both the Plus and Minus Terminals.

So I Wouldn't expect it to Burn it out, But Possibly it did.

The LM317 is NOT Current Limited on a DEAD SHORT, So it is More Likely the LM317 would get Damaged!

 

[Zabb Csaba]

Short circuit currents of LM317/117 series (internally limited current and power dissipation):

Regards.

 

[protocol217]

from datasheet of my LED i saw that anode and heatsink are connected:
**broken link removed**

and my lm317 driver i tested it with multimeter set to measure amps, when i put one terminal of the multimeter on minus of the battery and the other terminal to output of the driver,
and connect the input of the lm317 driver to positive of the battery, it is shorted out by the multimeter that way an it reads 0,82 amps = 820 ma
so it is shorted out and still limiting the current but it gets hot, i mounted the lm317 on a heatsink with 5 x 5 fan on it.
The diode probably died because it was shorted out and caused spikes in current and produce large reverse-voltage spikes as Zabb Csaba said above.

i will order a new led ( infrared again probably 940 nm ) and next time be careful with all the contacts

 

[tvtech]

OK...a change of subject here..(Briefly)

Nice cellphone tower and all you have now Gary:
http://chemelec.com/2014-CellTower/CellTower.htm

Take it easy,
tvtech

 

[chemelec]

from datasheet of my LED i saw that anode and heatsink are connected:
**broken link removed**

and my lm317 driver i tested it with multimeter set to measure amps, when i put one terminal of the multimeter on minus of the battery and the other terminal to output of the driver,
and connect the input of the lm317 driver to positive of the battery, it is shorted out by the multimeter that way an it reads 0,82 amps = 820 ma
so it is shorted out and still limiting the current but it gets hot, i mounted the lm317 on a heatsink with 5 x 5 fan on it.
The diode probably died because it was shorted out and caused spikes in current and produce large reverse-voltage spikes as Zabb Csaba said above.

i will order a new led ( infrared again probably 940 nm ) and next time be careful with all the contacts

I Really Doubt a Spike like that would burn it out, Unless it was a LONG Pulse of Current.
Usually you can PULSE Led's at Currents Much Higher than there Rated Current, For Very Short Periods of times.
I have successfully Pulsed 20 mA Led's with Short Bursts of 250 mA pulses.

But get that New LED and be more Careful next time.

As another Point, Your LM317 SHOULD have Both Input and Output Capacitors for Stable Regulation.

 

[tvtech]

I tried...no help

 

[Zabb Csaba]

Hi protocol217,

You will protect the new one from reverse-voltage spikes with an anti-parallel Schottky diode (1A).

Regards,
Csaba

 

[chemelec]

OK...a change of subject here..(Briefly)

Nice cellphone tower and all you have now Gary:
http://chemelec.com/2014-CellTower/CellTower.htm

Take it easy,
tvtech

Yes and it is Working Now for cell phones.

Now Waiting to see what they are going to charge for High Speed INTERNET Service Via the Cell Tower.
Seeing as Everyone in this town is Only a Maximum of 10 Blocks away from the Tower, It should be REALLY GOOD HIGH SPEED INTERNET.

 

[protocol217]

what diode should i order from these three:
1. https://eu.mouser.com/ProductDetail/OSRAM-Opto-Semiconductors/SFH-4725S/?qs=sGAEpiMZZMtjb30GAx/DTysazVSbpD%2beM%2bx6sQnjBl0=
heatsink for it? https://eu.mouser.com/ProductDetail/Bergquist-Company/804087/?qs=sGAEpiMZZMskHH4GZdiYeHsshxT2QnT%2bAeJEjbzRVqM=

2. https://eu.mouser.com/ProductDetail/OSRAM-Opto-Semiconductors/SFH-4239/?qs=sGAEpiMZZMtjb30GAx/DT3n/sHtdOQfXrC12hPxvwr8=

3. https://eu.mouser.com/ProductDetail/OSRAM-Opto-Semiconductors/SFH-4233/?qs=sGAEpiMZZMtjb30GAx/DT3n/sHtdOQfXjXiRRrBgHtY=
heatsink for it: https://eu.mouser.com/ProductDetail/Bergquist-Company/803128/?qs=sGAEpiMZZMskHH4GZdiYeHsshxT2QnT%2b9m%2bqzTsNBaM=

i want the brightest diode, i think the first one is good but i am not shore for the heatsink is it for that diode, it says that it is Designed for: Osram OSLON and on the diode page it says that diode is 940nm OSLON Black.

i want 940 nm because i will use this with my night vision, and i don't want to be visible much with naked eye, but want to be able to illuminate objects on 100 meters from me, so what diode should i chose.

they are all 1A maximum Forward Current and the lm317 will be with 1,5 ohm resistor again
and will supply 1,25 / 1,5 = 0,83 A = 830 ma running them on 83 % of power.

and can you draw me in paint a diagram where i should put those Input and Output Capacitors for Stable Regulation, and that anti-parallel Schottky diode for protecting from reverse voltage.

 

[chemelec]

SH47255, This one has the Highest Wattage rating
Power Rating: 3.4 W
Forward Current: 1 A
Forward Voltage: 2.8 V
I Think it is Actually 2.8 Watts.
But Reading it, it does say MAX of 3.5 Volts.

All those Heat Sinks Look Pretty Small.
Hopefully you have GOOD Ventilation.

I Haven't used any of those Infrared led's.
But on the 10 watt White Led's I have, I just Epoxyed 3 of them to a reasonable sized, Aluminum Plate.
Used as an Outside Light and has Been running Continuous for over 1 month now.

 

[tvtech]

Gary...

Crazy tvtech here: I say again" WELCOME BACK". It's probably "really cold" now!!!
I am freezing here in Africa...

All the best,
tvtech

 

[protocol217]

i will order SH47255 ( the first one ), the heatsink is for it i checked, and that small heatsink goes in a larger one and then will be coaled, that's not a problem.

no i just need now i drawing of driver, where i should put those Input and Output Capacitors for Stable Regulation ( and what values ), and that anti-parallel Schottky diode for protecting from reverse voltage.

 

[chemelec]

NICE HERE TODAY, 26 Celsus.
Supposed to be 30 Tomorrow.
Guess I can put my IGLOO Away.

Not sure Why the WELCOME BACK, I have never really been Gone.
I monitor about 6 discussion forums, but I don't reply to topics that don't interest me.

 

[chemelec]

i will order SH47255 ( the first one ), the heatsink is for it i checked, and that small heatsink goes in a larger one and then will be coaled, that's not a problem.

no i just need now i drawing of driver, where i should put those Input and Output Capacitors for Stable Regulation ( and what values ), and that anti-parallel Schottky diode for protecting from reverse voltage.

Ideally 1 uF Tantalum Caps.
(Or 0.1 uF Polyester Cap if you can't get tantalums.)
One on both the Input and Output to Battery Negative.

Diode, I just use a Regular 1N4001 Diode.
But you could use a 1N5819 Schottky diode.
Diode Line Side to Input, Other Side to LM317 Output.
(Not the Adjust Output as needed for the Current Limit.)

 

[tvtech]

NICE HERE TODAY, 26 Celsus.
Supposed to be 30 Tomorrow.
Guess I can put my IGLOO Away.

Not sure Why the WELCOME BACK, I have never really been Gone.
I monitor about 6 discussion forums, but I don't reply to topics that don't interest me.

Think of it this way.....a bit of happiness helps..like a spark somewhere...like WOW that Forum likes me??

Over and out if you don't get it.

 

[Zabb Csaba]

An input bypass capacitor is recommended. A 0.1 μF disc or 1μF solid tantalum.
The LM317 is stable with no output capacitors.
Protect the LED with fast Schottky diode. Place the diode as close to the LED as possible.
There is no need for protection diode(s) for the LM317 in this application.

All the best,
Csaba

 

[protocol217]

thanks for the final driver diagram, I ordered everything i need it can take up to 30 days to be delivered so will report back then.

 

[protocol217]

i ordered this diode from here: http://de.rs-online.com/web/p/led-ir/7732880/
data sheet: **broken link removed**

it is the same diode only mounted on a heatsink, i also fount a small driver for white cree q5 diode it is on a board 18 mm in diameter, and it gives 1060 ma i measured with multimeter when white led was glowing. it works with ONE 3.7 v li-ion baterry
is 1060 ma too much for my ir diode that i ordered or should i stick with my lm317 homemade driver, i don't want it to die again like the last one ?

here are the pictures:
**broken link removed**
**broken link removed**

 

[Zabb Csaba]

Hi,

Unfortunately I cannot see exactly what is on the picture but I think it must not be a current generator.
But it can be current sensor which may be needed if you use the factory power supplies suggested to the diode.
Currently it doesn't work for you. So you need the external current generator(LM317) and do not connect the LED directly to the battery. I found this in the PDF:
"Do not operate PowerStars with a Power Supply with unlimited current. Connection to constant voltage Power
Supplies that are not current limited may cause the PowerStar to consume current above the specified maximum and cause failure or irreparable damage."

Regards,
Csaba