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05-21-2008, 12:48 PM #1
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Volts, amps, and diodes- how much can it handle?

This is about these modules I got: dealextreme.com/details.dx/sku.10091

I have some old power supplies from telephones and other electronics that I am using for my diodes. Here is the output of some of them: (some pictures of them here: flickr.com/photos/26793374@N07/
OUTPUT: 5V 1A
OUTPUT: 5V 2A
OUTPUT: 5V 2.6A
OUTPUT: 4.5V 400mA
OUTPUT: 4.5V 600mA

I don't understand these differences in amps and volts. See how some are 5Volts, but each one has different amps. Does that mean that 5V 1A might work fine for a diode, but if I use another one with more amps like 5v 2.6A that will burn out the diode?

Sometimes, when you buy a diode, there is a label that says for example 5Volts. Does this mean that 5 volts is the limit for that diode? But what about amps? 5V and how many amps?

What is the output of 2 D batteries connected together as shown below? It will be: 3V - but how many amps?

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05-21-2008, 01:08 PM #2
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Re: Volts, amps, and diodes- how much can it handl

Each and every one of those chargers will most likely kill your red diodes instantly. : 2 D cells = 3V, current is calculated with Ohm's Law depending on resistance.

05-21-2008, 01:59 PM #3
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Re: Volts, amps, and diodes- how much can it handl

I got another power supply with this output: 3.7V 340mA
Is this safe to use for those diodes without destroying the diodes?

05-21-2008, 04:52 PM #4
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Re: Volts, amps, and diodes- how much can it handl

All those power supplies are voltage-regulated. the current they rate is what you may use without blowing up the power supply. The electronic thing you are powering with the power supply will decide the current that will flow, not you. Every fixed electronic thing will demand a fixed amount of current, depending only on the voltage and maybe temperature. For clarification, current is ALWAYS a result of voltage, physics dictates this.

Current is what kills electronics, so your power supplies have a maximum current rating. Exceeding this current will cause excessive heating, eventually killing it. Because every electronic thing is different, there are lots of things you can power with the same voltage without exceeding this current.

Laser diodes, on the other hand, should be powered with constant current. The delivered voltage should be a function of this current. Is this possible? yes. There are circuits which measure the current, adjust the voltage up if the current is too low and vice versa. This will not violate physics as current is still a function of voltage, a changing voltage in this case.

There are also current limiting configurations, which change the slope at which the current increases when the voltage increases. This requires a lot of knowledge about voltage-current curves. In case of laser diodes this a discouraged approach so I will not bother you with the details.

Lasers which state &quot;5V&quot; must have a driver built in, and as such should not be confused with (laser) diodes. This is indeed the maximum voltage, and also the recommended voltage (giving less is harmless but the laser won't function optimally). The current that will flow depends on the laser, and the only way to know it is by trying and measuring it (or read it from somewhere, because someone else already did)

Seriously, there should be a sticky thread about electronics basics or something, because people keep asking the same questions.
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05-21-2008, 11:08 PM #5
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Re: Volts, amps, and diodes- how much can it handl

Thanks for that information. Yea there should be a tutorial somewhere here explaining the basics about lasers, diodes, electronics etc. There should also be a glossary with definitions about all the commonly used laser terms, acronyms, etc.

05-22-2008, 12:49 AM #6
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Re: Volts, amps, and diodes- how much can it handl

there is, check the FAQ
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