Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers

LPF Donation via Stripe | LPF Donation - Other Methods

Links below open in new window

ArcticMyst Security by Avery

Driver Design.

kiyoukan

kiyoukan

0
Joined
Oct 24, 2009
Messages
2,555
Points
48
I am looking at making a simple yet working linear driver.
My only things are.
I don't want to have to use high wattage resistors.
Able to go up to 2a.
Now i like the idea of the amc7135 but they are 600 short of my goal.
So i went on the hunt.
Now i can get any ic i could very well dream from ST micro for free.
So i was looking at what is the minimal i need to drive some nice high powered lasers.
The 445nm laser need at least 4.2V so i chose and output of 5V and at least 200ma.
That is correct that's the minimal needed current and power?
So upon my searching i have found a few ics but only one jumped out at me.
http://www.st.com/stonline/books/pdf/docs/4337.pdf
http://www.st.com/stonline/products/literature/ds/2142/l4941.pdf
it outpouts 5V at 500ma with a dropout of only 0.4v.
I was thinking of using this as i could mount one and get 500ma 2 and get 1000 and three to get 1500 and 4 to get 2000.
This board would look just like the amc7135s but with a little more power.
So what do you guys thing will this be able to handle and run off 2 cr123a 3.5v?
just found this super low dropout
http://www.analog.com/static/imported-files/Data_Sheets/ADP3338.pdf
 
Last edited:





Vaporizer

Vaporizer

0
Joined
Aug 6, 2010
Messages
382
Points
0
Dx has the multi boards with the amc7135's 3 & 4 per board. The reviews show they can be paralleled. Thats how they are on the board. 6 paralleled would give you 2250ma. so you could put 2 boards back to back and parallel the 3 main lines or sand the battery contact side free of tracing glue 3 to that side and drill holes so you can parallel them the the existing pcb.

Seems simple and cheap for a no resistor driver.
 
Benm

Benm

0
Joined
Aug 16, 2007
Messages
7,896
Points
113
Both chips are voltage regulators, not current sources, so they wouldnt be a very good source for building a laser driver.

I suggest building a proper opamp based driver circuit - no need for adjustable power resistors to set current, and the costs and component count are rather limited. The drop out voltage can be under 1 volt when well designed, and even pushed a bit below that when using mosfets instead of transistors as the current handling component.
 
Benm

Benm

0
Joined
Aug 16, 2007
Messages
7,896
Points
113
I meant the two regulators he linked, not the AMC7135. Those are current regulators indeed, and can be paralelled to get more juice in increments of 350 mA. A problem is that you cannot reliably run this chip from 2 lithium batteries as its max supply voltage is 6 volts. I guess this could be remedied by a couple of drop diodes in the vdd line.
 
BShanahan14rulz

BShanahan14rulz

0
Joined
Dec 29, 2009
Messages
3,136
Points
63
BenM, would you happen to know if dropping the extra voltage to the Vdd line but not to the actual load would have any adverse affects?
 
Last edited:
Vaporizer

Vaporizer

0
Joined
Aug 6, 2010
Messages
382
Points
0
Benm, My bad, I though you were including all of the ones in the OP. I have a few amc7135's coming. I want to test them myself. A reverse protection diode and I think an output cap are warranted too. They run LED's, but I'm curious to see if the output spikes.
I read this one confusing post abt the amc7135 not being able to work with an output cap, but then they claimed to use it in a LD driver situation.
One of those to many unanswered questions thing so I'm gonna see for myself.
Alone, your stuck to 350ma or stacked multiples of 350. Might be possible to control or even dump a few ma's on the output to allow them to have those in between outputs one might want.

Edit: The RCR123A can be bought as a 3v not 3.7v. Diodes wouldn't be needed with these. I have 2 of them in transit too.....lol
 
Last edited:
Vaporizer

Vaporizer

0
Joined
Aug 6, 2010
Messages
382
Points
0
They make 2 diff compounds in that battery. One is a Li-Ion and the other is LiFePO4.
I've seen them as high as 900ma and you have to be careful even using the correct charger as there have been issues. If memory serves me correctly the discharge on the "Fe" type is strange.
The OP was addressing the possible use of the AMC7135 as a LD driver and it requires a 6v input. Just to try it the input voltage is going to have to be 6v by one means or another. If it does work the user will have to determine the conditions they are willing to live with to use it. You could use 2 of the 3.7v Li-Ion and a LM350 3A voltage regulator to run it.
 
kiyoukan

kiyoukan

0
Joined
Oct 24, 2009
Messages
2,555
Points
48
my current regulators are comming in today. i wonder how they will preform.
i know they are not ideal but i think they should work.
 
Vaporizer

Vaporizer

0
Joined
Aug 6, 2010
Messages
382
Points
0
If they are the 7135 or whatever you did get, pls post it. If it works with a protection diode and a cap on the output it could be used in certain places and be fairly small, inexpensive. Another outlet for a possible driver is good. That's why I ordered them.
If they don't, they'll get used on something I make. lol
 
kiyoukan

kiyoukan

0
Joined
Oct 24, 2009
Messages
2,555
Points
48
i did not order any 7135s
I ordered the other 3 i had listed.
From what i have read another in other posts they work great.
 
You must log in or register to reply here.




Top