Why NOT to test your diodes on batteries!

[JLSE]

I found it surprising, as I have a red pointer that I fitted with an LCC from a 6x drive and have had it for ages. I had always gone through more batteries to keep the output high, and have gone through many of the batteries that come with DX greenies.

They are probably as generic as it gets, yet the pen lives.

What diodes did he kill? Im getting the feeling senkat 16x? Cant remember.. I think I saw that thread..

If 16x than thats a bit different. Whats the max mA on those? 250mA or something?
Im reffering to LCC, which may explain my difference of opinion.. They can handle double the current.

Got a link?

 

[RJD]

I found it surprising, as I have a red pointer that I fitted with an LCC from a 6x drive and have had it for ages. I had always gone through more batteries to keep the output high, and have gone through many of the batteries that come with DX greenies.

They are probably as generic as it gets, yet the pen lives.

What diodes did he kill? Im getting the feeling senkat 16x? Cant remember.. I think I saw that thread..

If 16x than thats a bit different. Whats the max mA on those? 250mA or something?
Im reffering to LCC, which may explain my difference of opinion.. They can handle double the current.

Got a link?

They were the 20x LOCDs and the VERY FIRST one was installed with a driver and failed, only after did I test the remaining ones. But that is old news I am learning more than I originally knew about batteries in this thread so lets try to keep it limited to useful information that we all can learn from!
:gh:

 

[lasersbee]

1)You are not getting 8.8 amps from any AA battery! I am not correcting you to argue. I just want to explain to anybody reading this why it is incorrect information!

Ok first thing your trying to read amps 2) on a battery that has less than 1A so 3) you need to switch your DMM to 200m in the dc amp range, 4) Now that your trying to measure the amperage in the correct range you will get a more accurate reading!
5) Batteries are rated in MILLIAMPS not amps. If it were true that your AA battery had a current of 8.8 amps that would eqaute to 8800 mA. 6) There is no AA battery that I know of that has that kind of amperage!

There is an easy way to check this with or without a meter! 7) If you do not have access to a DMM but know how many milliamps your battery is!
As a milliampere (milliamp or just mA) is 1/1000th of an ampere, we can convert mA to Amps by just dividing by 1000. Another way is to take the current in mA and move the decimal to the left three places to accomplish the division by 1000.
mA / 1000 = Amps

Here is my photo taking a milliamp reading note the position of the selector switch

8) So this brand new Duracell has 1/4 of 1/1000th of an amp or 25 mA!
This is all easy to prove using the basic rules and formulas that govern electricity. There is no sense :horse:and my only intent here was to correct the missinformed in regards to battery amperage!

Here is an example of how to obtain a incorrect reading on a DMM. Using that same Duracell in the pic I switched my DMM to ACV 200 and took a reading, the results 2.5 ACV! This is obviously incorrect that is why you must be sure your taking readings in the correct range!
No slight intended and hopefully no hard feelings
and thanks for reading!

I have never read such blatant misinformation in my life...
Either he really believes what he posts or he is a TROLL....

And what is he doing back on the Forum... Ohhhh Moderator....

1) The OP IS getting 8.8 amps from a 1.5Volt Alkaline AA battery... even if it
is for only a short time..

2) Alkaline batteries can easily supply 10 Amps in shorts bursts...
(see reading on Meter in 1st Post)

3) switching to the 200 Milliamp Scale will only result in blowing the
fuse on that scale

4) it is the WRONG Scale

5) Batteries are not measured in Milliamps... Battery capacity is
measured in MilliAmpHours (Mah)

6) See photo in the first Post....

7) Gee... Thanks for the 3rd grade division lesson

8) For someone so arrogant and spewing so much misinformation...
you should perhaps take a course in basic electronics and proper
electronic instrument usage...
You have no clue as to how to use a simple DMM... maybe you would
get more accurate readings on the 200m scale if you unplugged the
Positive lead from the 10 Amp jack and plugged it into the proper
Volt/Ohm/mA jack. (see your own photo)...

I will guarantee that you will need to replace the Fuse in your DMM...


[EDIT]
I was so enraged by that Idiotic useless post that I didn't read the posts
following.... "lazerov" had basically posted the same thing...


Jerry

 

[photonaholic]

Before you reply Robert, Lasesbee is CEO of an electronics firm, and is an engineer of electronic circuits, so be really careful with that reply.

 

[lasersbee]

He doesn't need to be careful....
just a bit more accurate and factual with his "knowledge" he is presenting...
Up to now... I'm not too impressed with it...

BTW... there are many members here that are a lot more knowledgeable
than myself..


Jerry

 

[photonaholic]

Jerry, there may be others more knowledgeable in many things than you are, however I respect you, I consider you a friend, and as you already know, I will not sit idle and watch someone who clearly does not even know how to use a DMM properly challenge your word when your field of expertise is in electronics.

 

[LSRFAQ]

Laser diodes have a voltage vs current curve. conduction starts about 1.5 volts on some diodes. And its up the curve to 2.4 -3.00 V or more for a red one at rated current. But should you have a hotter battery, you going to drive the diode harder and harder into conduction, and it can avalanche to the full current of the battery, limited only by the batteries internal resistance. Try that with a good lithium and you'll smoke them every time.

Without some form of current limiting, your playing Russian roulette with the diode.

Since the diode reacts in about 15 nanoseconds, there is no "Saving" it if it pops, and odds are you kill some so fast you never see it flash.

steve

 

[lasersbee]

Hey Steve...

I think that the explanation of the pitfalls of using just a battery to drive LDs
may be a bit too technical for a guy that doesn't know where to plug his DMM
probes on the DMM...

Jerry

 

[Anthony16r]

Is there any way then to safely and simply test a laser diode before mounting it on driver ect...?

 

[lasersbee]

As a matter of fact you can use any current limited driver set at just
above the Threshhold current of the LDs you want to test...

The Threshhold current is the lowest current that is required by the
LD to start Lasing...


Jerry

 

[charliebruce]

You could use the diode test function of a multimeter to verify it hasn't totally blown, but there's no real way of testing unless you can get a reliable and easily-attachable constant-current source that doesn't risk blowing a diode, even if used improperly. Easier to just solder it to a driver IMO.

 

[Benm]

Its always tricky using a current source. They will always put out supply voltage when not connected to a load, so the load always gets a bit of a jolt when connected hot. How big the jolt is depends on whether there are any output caps, and if so how large they are.

Something like a LED tester isnt likely to have much output buffering and can be used to check LD's too. I still recommend soldering a driver on and then powering that up. Its a one minute job, and only problematic if you have to check large numbers of diodes.

 

[Tech_Junkie]

How about AAAs?

I've, and others, have had red diodes hooked straight to 2 AAAs without issue. Mines been going to at least an hour now.

 

[daguin]

How about AAAs?

I've, and others, have had red diodes hooked straight to 2 AAAs without issue. Mines been going to at least an hour now.

It depends on the batteries and the diode. Some batteries have more internal resistance than others. Some diodes will take more abuse than others.

The main idea here is that hooking up a diode to a battery is not a good idea (unless that battery is well below the diode's draw). They MAY be fine. However, more often than not, they will blow immediately or fairly quickly.

Hence the blanket recommendation that one should NOT hook a diode directly to a battery.

Peace,
dave

 

[Things]

AAA's are still good for a few amps for a short time, however obviously they won't supply as much as say an AA.

A simple way to test diodes without a driver is to buy an LED tester. They have currents up to about 50mA, which is usually enough to get a diode lasing atleast. If not, connect a few other currents in parallel.

Like this: LED Tester Multi Function Module M087 - Jaycar Electronics

 

[Tech_Junkie]

Not bad, cheap too. I may get one, I have a pile of LEDs too that can use checking.