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Here is the third installment of the ongoing saga of my failures at interpreting circuit diagrams and other completely basic things...
Anyways, today I decided to try making a driver out of whatever parts I had laying around... I found this regulator in an old laptop and a few cdrom drives I had... It says it handles up to an amp and has a low dropout voltage, so I thought it could work out well... After a few false starts I've built the circuit laid out in the reference schematic I found in the datasheet and it seems to work the way it should... I did have a couple problems though...
I used a couple LEDs as a dummy load and found 175-200ohms across the pot lets the LEDs draw 275-350mA, so I set it around there and put in one of my useless rectangular 16x diodes... When it's first turned on it draws around 400mA for about a second, then drops to around 290... then if you let it sit, the current slowly drops till it reaches about 160mA and settles out. Interestingly, I didn't notice a real drop in light output...
I figured this was probably something thermal, so I soldered a penny onto the laser, and another onto the regulator to sink the heat... Sure enough the current became much more stable and stayed around 300mA. After about 5 min of running I checked the pennies for heat buildup and the diode had barely made the penny warm at all, whereas the regulator's penny was scorching hot and my skin sizzled when I touched it.
These regulators are supposed to be rated up to 1A, so why is it getting so unbelievably hot at 300mA?
Is there a fundamental difference between this voltage regulator, and say, a lm317t (presumably a current regulator of some sort)??
Anyways, today I decided to try making a driver out of whatever parts I had laying around... I found this regulator in an old laptop and a few cdrom drives I had... It says it handles up to an amp and has a low dropout voltage, so I thought it could work out well... After a few false starts I've built the circuit laid out in the reference schematic I found in the datasheet and it seems to work the way it should... I did have a couple problems though...
I used a couple LEDs as a dummy load and found 175-200ohms across the pot lets the LEDs draw 275-350mA, so I set it around there and put in one of my useless rectangular 16x diodes... When it's first turned on it draws around 400mA for about a second, then drops to around 290... then if you let it sit, the current slowly drops till it reaches about 160mA and settles out. Interestingly, I didn't notice a real drop in light output...
I figured this was probably something thermal, so I soldered a penny onto the laser, and another onto the regulator to sink the heat... Sure enough the current became much more stable and stayed around 300mA. After about 5 min of running I checked the pennies for heat buildup and the diode had barely made the penny warm at all, whereas the regulator's penny was scorching hot and my skin sizzled when I touched it.
These regulators are supposed to be rated up to 1A, so why is it getting so unbelievably hot at 300mA?
Is there a fundamental difference between this voltage regulator, and say, a lm317t (presumably a current regulator of some sort)??