Driving a Red Open can with DX AMC7135 350mA

[LiveRock]

Hi

I read somewhere that to drive a red open can with AMC7135 350mA (http://www.dealextreme.com/details.dx/sku.3160)
means:

1. That I must reverse the battery
    If not, it will get shorted.

2. The current actually fluctuates with the input voltage

Question is: How to do the 'reversing of the battery' part? I also read that the LD case is touching the host casing and that is not good.

Also read something about output cap, reverse polarity protection is actually bad for the LD.

Frankly, I am more than confused.... will someone come out with a tutorial how to do a 300-400 mw Red Open Can laser project using a typical host with the AMC7135 driver?

Many Thanks!

 

[ben74]

Yeah i would love to know more about the AMC7135 like can it power blu-ray diodes?

 

[billg519]

The 7135 is a negative side regulator. This means that it is placed in the negative side of the circuit, this is the opposite of an LM317, which goes in the positive side. Problems arise with this regulator with laser diodes that are can negative, because we usually set up our host to be negative ground, and the regulator goes between battery positive and the positive lead of the diode. Can't do this with a 7135. One solution is to electrically isolate the head of the laser from the body, so that both negative and positive leads must be run from the body to the head. If you have access to a lathe, this can be doable by making a plastic isolator adaptor ring.
Another drawback to the 7135 is that it does not like the presence of an output capacitor, the regulator will usually refuse to start up if a capacitor is present. The 7135 also needs to be connected to the positive supply.

The 7135 can be used to make a small red laser, but it can be challenging. You might be better off to either stick to an LM317, or order up a drlava or rkcstr driver, these are good options.

In the attached photo, the laser uses a 20x DVD open can red, a 350ma 7135 regulator, and a CR123 lithium as power source. The laser is 3" long by 3/4" diameter. Note the machined hard plastic ring between the head and the body. This host was completely custom machined, no aixiz housing either. Note the knurled brass focusing nut. Lens is aixiz acrylic. Laser switch is in the tailcap.

These 7135 based DX regulators are cheap, but in my opinion, best used for IR lasers where the diode is positive ground. For my 2w 808nm handhelds, I use 2 x 1400ma 7135 based DX regulators and they work great.

 

[billg519]

ben74 - The 7135 is not suited to bluray diodes. The maximum recommended voltage input to this DX driver is 4.5 volts. Even if it ran on a higher voltage, the 7135 does not like output caps. Use a better type of regulator for a bluray. LM317 and a 9v or 3 x 10440 works well. So do drivers from drlava or rkcstr.

 

[ben74]

Yeah i have ruined all the lava drives i have bought and rkcstr drivers... so i was trying to find something cheap :-/ i'll just keep looking

 

[Ironbar]

Yeah i have ruined all the lava drives i have bought and rkcstr drivers

Oh no! How did you ruin them?

 

[ben74]

Lots of stupid mistakes

 

[LiveRock]

output caps? Where it comes from?

From the AMC? where?

 

[ben74]

Here they are http://www.dealextreme.com/details.dx/sku.3160 and the output cap http://parts.digikey.com/1/parts/44498-cap-47uf-25v-elect-ky-rad-eky-250ell470me11d.html or you could use a tantalum capacitor of the same value.

 

[ben74]

Anyone know what resistor i need to get 420mA from a AMC driver? and how is it figured out?

Sorry for the old thread but it's better to bump than start new threads (that's what i think anyway)

 

[Benm]

The AMC is a fixed current driver with no resistor to set its current. It will run whatever load connected to it at ~350 mA - mainly intended for powering power LEDs rather than lasers.

 

[nmbusa]

Anyone know what resistor i need to get 420mA from a AMC driver? and how is it figured out?

Sorry for the old thread but it's better to bump than start new threads (that's what i think anyway)

I made this little pocket rocket based on a amc7135 350ma.
added a second chip and a 1ohm resistor in series and is at around 460-480 ma from what I remember.LG22x loc.

 

[nmbusa]

Yeah i would love to know more about the AMC7135 like can it power blu-ray diodes?

I made an easy project PHR violet based on amc7135 350ma for a friend real cheap.
since host powers by 3 AAA alkalines dropped output to about 200 ma with an smd 8.2ohms resistor in series as alkalines tens to sag really quick.

 

[Benm]

Driving a blu-ray using the AMC is not recommended, though i think it could be done.

The trick would be to introduce a couple of diodes between the actual supply voltage (say 7.2v from lithiums) and Vdd on the AMC. This way you stay within the operating parameters of the AMC, but you can get some extra voltage for the laser diode.