small lm317 driver advice needed

[BShanahan14rulz]

For a blue build, I actually might have to recommend against the 7135's, because once the battery voltage under load drops below (Vf+0.12V), it essentially acts as direct drive, i.e. your output starts dropping as the battery depletes past Vf+0.12V.

If you are running it at 1.4A, your Vf would be in the upper end of 4V.

I've wanted to experiment with using diodes to drop the 8.4V to 6V going to the Vcc pin, while keeping the full 8.4V available for use by the load. I can't say if this will work or not, but it's worth a shot.

Alternatively, you could source some 3.0V RCR123's (yes, there is such a beast) and just use those to power your light. Just try to use protected if you can, because you'll be drawing 1.4 amps from the cells, and that's just a wee bit over the 2C recommended limit for Li-Ion.

 

[kiyoukan]

there is this so it can use higher voltages right?
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[lazeerer]

I have been using this driver >>>HERE<<< with 2 Cr123A 3.6v batteries and it sits at around 1200mA.

I think its an awesome driver for the 445nm if you want to drive it at 1200mA. Just use 3.6v Cr123A and you will be stable at around 1200mA. This driver will not work with 1 18650, Well is does but you only get 180mW.

Hope this helps and nice build.

 

[BShanahan14rulz]

the netkidz/download hack drops overall supply voltage, taking advantage of the fact that the 7135 is a linear driver. You'd want to, drop the Vcc voltage w/o also dropping the supply voltage.

I'm semi-busy right now, but this week if I have time, I'll draw you up a doofy MSPaint diagram if you'd like.

 

[Vaporizer]

Well, the RCR123A 3.0V Tenergy batteries seem to be the highest I can find @ 900ma. So you would be pushing them hard @ 1.4A draw. They aren't cheap either. The less expensive brands go as low as 350ma. If you go with 2 RCR123A's be sure you get the best ones.

BShanahan14rulz, are you considering running the circuit on the full 8.4V, isolating the 7135 Vcc with 4 2A diodes in line to drop just the 7135 regulator down to 5.4V?

Edit: The 7135 is a stand alone regulator so there is "no other part" of the circuit unless you added a current regulated MOSFET.

 

[tuzvihar]

BTW Did you guys know that you can order free samples from Texas Instruments?
Analog, Embedded Processing, Semiconductor Company, Texas Instruments

You can order 5 pieces of the same component and maximum 8 different items (5*8 total), they will ship it free and it is very quick. I ordered several times from them, and it arrives in 2-3-4 days even to Europe.

They also ahve LM317s and many types of linear and switching regualtors.

 

[Vaporizer]

Linear Technologies has a free 5 part offer too.

 

[BShanahan14rulz]

Vaporizor, that's what I was hoping to do, but haven't had time to see if it actually works. I kind of worry that the 7135, for whatever reason, might take some sort of voltage reference between its Vcc and output pin, and if it does that, this idea might not work.

You understood exactly what I meant, what do you think about that idea?

 

[Vaporizer]

It was easy to understand from your description. Scarey, huh?

DealExtreme: $16.68 Quality AMC7135 350mA Regulated Circuit Board for DIY Flashlights 20-Pack
AMC7135's are capable of being ran "stacked" in parallel if heat sinked properly.
The AMC7135 is a stand alone fixed regulator. It has no support components other than the reverse protection diode unless it has the mode switching chip.(from DX page) Also, the voltage ranges are all over the place on DX pages. As are the comments......check comment #2(ben73) on the page above. :wtf:

The AMC7135 spec sheet states a max voltage of 7V and a dropout of 120mv! The current output is not adjustable.
http://www.micro-bridge.com/data/ADD/AMC7135.pdf

Surfing the net I've seen these referred to in laser builds. A 7805 could easily regulate the input voltage to 5v wasting a little voltage to heat.
I think for a 1W build or lower, they have promise. Seems they would be a cheap solution to specific builds.

I'm gonna get DealExtreme: $6.97 3.6V~9V 800mA Regulated IC Circuit Board for Cree and SSC LEDs (4-pack) & DealExtreme: $1.99 18V 5W Cree Circuit Board for Flashlights (16.8mm*5.5mm) and a couple boards with the 3 7135's. That should give me a bunch of possibilities to experiment with. There are tips on changing the output of the 1st 2.