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I am pretty sure I can fit a 47uf cap in parallel directly soldered to the diode, and then maybe a 1 ohm resistor in series with it, if I did this will it protect the diode better than just direct current?
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ArcticMyst Security by Avery
MiniMag mod?
- Thread starter goldfingerfif
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Chad said:
What do you suggest? I came to 1 ohm based off of LED calculations, 3v source voltage, 3v forward voltage for the diode, and ~250mA. I was thinking maybe 2-5ohm but I was thinking 5 ohm would drop the voltage too much? I have the cap in there for stability from the batteries. Is 47uf too much or to little? I was thinking maybe bumping it to ~100uf
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Sounds good, maybe I'll put the LD, cap, and resistor on a bread board, hook up power and try different resistor values while monitoring voltage and current with a multimeter.
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How to calculate the resistor in ohm:
The power voltage, minus the forward voltage, divided with the current in amps, not ma.
Ex. 5v - 3v = 2 / 0.04 (40 ma) = 50 ohm
Hope this helps in the future.
The power voltage, minus the forward voltage, divided with the current in amps, not ma.
Ex. 5v - 3v = 2 / 0.04 (40 ma) = 50 ohm
Hope this helps in the future.
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FireMyLaser said:
Not sure who this is too, but, 3v (input, 2 x 1.5v AA) - 3v (forward volts of LD) = 0 / .250 = 0 ohm
This is why I was thinking 1 ohm, I am scared anything more will drop the voltage by too much to make the laser burn.
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A frech battey has a little more voltage then 2 x 1.5v, I think. So make it ~4v.
4 - 3 = 1 / 0.25 = 4 ohm :
If you use 1 ohm with 4v it will have 1 amp through it!
Anyway, I think that you should use a good driver if you want it to last
4 - 3 = 1 / 0.25 = 4 ohm :
If you use 1 ohm with 4v it will have 1 amp through it!
Anyway, I think that you should use a good driver if you want it to last
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FireMyLaser said:A frech battey has a little more voltage then 2 x 1.5v, I think. So make it ~4v.
4 - 3 = 1 / 0.25 = 4 ohm :
If you use 1 ohm with 4v it will have 1 amp through it!
Anyway, I think that you should use a good driver if you want it to last
Yes I know I should use a driver, thanks for the advice, and I have even built a few drivers now. The minimag is so nice instead of a big stupid box to house the laser. Problem is you sacrifice the diode life if I use no driver for looks and portability. If you hook it direct it will die quickly, I figured 1 ohm is better than 0 ohm. I was just wondering basically if:
1. Doing this would make a difference?
2. Is that a good cap value?
3. Is it a good resistor value?
Answers so far seem:
1. Is a Yes
2. Yes
3. Seems like I would want 2-4ohm instead of 1ohm depending on fresh battery voltage.
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I see what you mean. How about using 2 x 3,6v AA and make some new calculations from that. At least you have more room for the variables.
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FireMyLaser said:
I have never seen a 3.6v AA but maybe I'll have to check a specialty shop. That would allow more voltage and amps to be burned off by the resistor. Thanks, that will be something to look into.
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DX has them [smiley=smiley_down.gif]
http://www.dealextreme.com/details.dx/sku.975
Note: full charge: ~ 4.2v
http://www.dealextreme.com/details.dx/sku.975
Note: full charge: ~ 4.2v
Gazoo
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You can use a 10uf 16 volt cap which would be much smaller. The SenKat diode running at 3 volts is drawing appx. 250ma's. You should be fine with a 1 ohm resistor provided you use alkaline batteries and stick with them. You could use nimh batteries and it would still lase but the power output would drop considerably. If you used primary lithiums I don't think the diode would last very long. This is why it is best to use a regulator...to keep the current going to the diode constant. You might want to consider the MXDL mod instead.
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Gazoo said:
I have 2 MXDL housings and they are nice but not like the Minimag. I am trading the MXDL's away to Jake21. I had a diode in the minimag with lithium e2 AA's and it burned out after being on for ~3hrs. I want another solution for now, and want a little safety but I learned of some mistakes I made. I think this might suit my needs until more MXDL housings get to my house.
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You would need to get a higher resistance value, the recent senkat diodes have been dying within a week at 250ma, if you bought it sort of recent that that is probably the case and you should not go over 180ma
The cap value in there is fine. Also make sure you know how to measure current right, you cant just set it to current and put it in paralel in the circuit, it will more than likely kill it.... take a 1ohm resistor put it in series then put each of the leads on seperate sides of the resistior and set the meter to measure mv... the resulting reading will be what ma its drawing.
..lazer... ;D ;D ;D
The cap value in there is fine. Also make sure you know how to measure current right, you cant just set it to current and put it in paralel in the circuit, it will more than likely kill it.... take a 1ohm resistor put it in series then put each of the leads on seperate sides of the resistior and set the meter to measure mv... the resulting reading will be what ma its drawing.
..lazer... ;D ;D ;D
