CR123A housing HAS blue ray.

[zerafiel]

Re: CR123A housing awaits blue ray.

Ok. I'm gettng confused again.

catdog says it needs 12v if running as a current regulator

But you say the vdrop is only 1.7v. Or are you saying that rog is going to use the 7805 with a series trimpot which will drop the 5v output further depending on the diode.

 

[Gazoo]

Re: CR123A housing awaits blue ray.

Rog is planning on putting a resistor in series with the diode. I am going to do the same.

 

[Daedal]

Re: CR123A housing awaits blue ray.

Well... sorry to be late to answer here... I did follow the thread and I LOVE... absolutely LOVE that case!! I am VERY jealous... :-[

As about the 7805... Hmm... let me think for a bit...

My understanding is that since the VOLTAGE is stable enough at the IC output, that a simple resistor can be used to regulate the current...

Filtering the battery output right before anything (including the 7805) will also help clear out some of the ripple and noise. Try placing a 100uF cap right at the Vin for the 7805 and connect it to ground (common to all the circuit and all the way to the battery).

With that done (especially since the cap is nice and big) nothing will go into the circuit other than what is intended to go in... and the 7805 will also do a better job. Out of the circuit a simple calculation using V = I * R where V is a constant voltage of 5V, I is a constant current of (XX)mA as you wish to drive your diode, and the R is the calculated value... so effectively R = V / I.

Simple enough

Now... for 35mA supply (recommended) that would give you ~143-Ohms.

GL all and let me know what you come up with or if you need any help.

--DDL

 

[zerafiel]

Re: CR123A housing awaits blue ray.

DDL I am not convinced by 5v/35mA=143ohm

That's what I thought initially. But looking at Rog's diagram his LD input is connected after the trimpot connected to the common pin.
Since there is a fixed 5V difference between the Vout and the common pin, there is a 5V drop there after the resistor leaving almost nothing for the LD. I am quite sure I am reading the diagram right.

Even if the Vout of the 7805 is always 5v regardless of the common pin, the diode won't see any useful voltage with 143ohm. At least that is the way I see it now.

Darn I gotta find a small enough screwdriver, where are my jeweler's screwdrivers?!

 

[Gazoo]

Re: CR123A housing awaits blue ray.

You need to look at the diagram when this is used as a voltage regulator. But I agree with you, I think we will find the resistor needed to be in the 5-15 ohm range depending on the forward voltage of the diode.

 

[zerafiel]

Re: CR123A housing awaits blue ray.

Yes. I mentioned 5-15ohm might get right current with about 4.5v depending on the diode. Still the only advantage this gives over driving with 6 volts + series resistor direct is a more stable input voltage. We might as well use a 6.2v regulator and use more resistance for better current tuning and voltage at the expense of input voltage.

 

[Daedal]

Re: CR123A housing awaits blue ray.

:-?

Hmm... and I'm the one who's been working on circuits all day... ha? ;D

Ok... you got me. I'll look into it... I think I have a 7805 sitting somewhere here... I'll try it out and let you all know.

--DDL

 

[Daedal]

Re: CR123A housing awaits blue ray.

Quick look at the data sheet...

--DDL

 

[Daedal]

Re: CR123A housing awaits blue ray.

I'll get the exact breakdown for this... hold on tight... brb

--DDL

 

[Gazoo]

Re: CR123A housing awaits blue ray.

This is the schematic I have been looking at...

 

[Daedal]

Re: CR123A housing awaits blue ray.

7805 is [smiley=thumbdown.gif]

Sorry... but it's not nearly stable enough to run as a current regulator... at least from what I've seen here and I've got 2 of them that I just unpacked and tested.

The voltage input makes a HUGE difference for the drive current... and in a situation where the 7805 gets a nice spike of about 15V on initial battery discharge, the current going into the diode could fry it instantly! :-/

It's just good as a voltage regulator, or a current regulator for a less sensitive application maybe. :

--DDL

 

[Daedal]

Re: CR123A housing awaits blue ray.

Whatever happened to the simple and stable Iout = 1.25 / R? ;D

It works, doesn't it?

The LM317 should be able to drive the diode down to a pretty nice voltage out of these RCR-123's... the current is low enough that the regulation would work just fine at a low Vin... I think... Let me go try that one as well... ;D

Ok, maybe tomorrow then... :

--DDL

 

[Gazoo]

Re: CR123A housing awaits blue ray.

Thanks Daedal...I found the same when I tried it as a current regulator..it did not regulate anything...lol. But I still feel it's safe to use with the blu-ray as long as it is used as a voltage regulator, with all the precautions mentioned before in this thread..

As I explained to you in my PM, and in this thread, the reason I wanted to use it is because I was able to get them for 10 cents a piece in a TO-92 case.

 

[Daedal]

Re: CR123A housing awaits blue ray.

Ok... not it doesn't... once the voltage drops below ~9V the current takes a quick dip and the pot would need to be turned down to compensate... and that's not a solution...

Maybe you guys should look into LDO's? :-?

--DDL

 

[Gazoo]

Re: CR123A housing awaits blue ray.

Not me...lol. Not unless the 7805 does not work, but I know it will. The 100ma one in the TO-92 has a drop out voltage of 1.7 volts. Rog is going to use RCR123's....the nominal voltage of two of those in series is 7.2 volts. I will be using a 9 volt battery for now.

 

[Daedal]

Re: CR123A housing awaits blue ray.

Those 9V's are killing me... :'(

The LPM is a battery hog and the 9V's in there is probably the worst idea EVER! I'm probably going to be spending some time getting a nice mod so that I could use better batteries in there...

And the BluRays should be getting a better power source... If all goes well... it shouldn't be too far away

--DDL