Couple of general electical questions....

[bhank]

Ok so I'm still very inexperienced when it comes to electronics and I've got a few questions for anyone that can help.

First off, for a capacitor, it does matter which way the current is going through right? I mean there is a + and - side. On the 10mfd 16v one i got the pins are the same length and I'm not sure how to tell which is which. Also, I know that microfarad is a measurement of the capacitance but if someone could explain to me in more detail that'd be great.

Second, for a potentiometer, rog8811's driver calls for a 100ohm potentiometer and I can't seem to find any at my local radioshack. Would any other resistance work as well or would that call for other values in the circuit to change as well?

Last, If I wanted to add an on/off push button switch, where would I place it in the circuit?

Like I said I am VERY inexperienced when it comes to electronics so if anyone can help clear some things up for me I would greatly appreciate it.

Thanks,
Blaine

 

[Benm]

Capacitors with + and - signs should be place such that the voltage across them follows the indicated order. If the capacitor is connected to the battery directly with either leg, make sure that leg matches up with the battery... or follow what is indicated in the circuit diagram.

A push button is likely best inserted in series with the battery. It can be in series with the positive or negative lead - that doesnt matter at all - but convention is to put it in the positive lead.

Farad is a term that describes, roughly, how much current you can store in a capacitor. If you were to envision a capacitor as a bucket that stores energy, more (micro)farads mean a bigger bucket.

 

[pseudolobster]

Some capacitors are polarized, others are not. If they have a polarity one side of the cap will be marked with a line or some other indication, usually meaning that's the negative side of the cap. If it's an electrolytic or tantalum cap it's probably polarized, though if it's a ceramic cap it's likely not. Farads are like you said, a measure of capacitance.. It pretty much means for how long it can sustain that charge, sorta akin to the mAh rating on a battery, only farads are based off an absolute charge in coulombs, and mAh is a given discharge over time.. But yeah, for more info on capacitors, read an encyclopedia or something

For a potentiometer, it doesn't really matter what rating it is, since it's adjustable after all, yet the higher the value the pot is the less fine tuning you'll be able to do... For the driver, the lower the resistance, the higher the current... If you use, say, a 10kohm pot, you'll be able to fine tune it really well between 1-10mA, but once you get into higher currents, such a tiny turn on the pot will cause a huge difference in current. I'd suggest using a 25ohm or 50ohm pot, preferably one with multiple turns, to give you some fine tuning ability.

As for a switch, put it between the batteries and the driver, don't put it between the driver and laser diode or bad things happen. Basically, hook up the - end of the battery to the - end of the driver, and have the + end of the battery go through the switch to the + end of the driver.

 

[jamilm9]

Some capacitors are polarized, others are not. If they have a polarity one side of the cap will be marked with a line or some other indication, usually meaning that's the negative side of the cap. If it's an electrolytic or tantalum cap it's probably polarized, though if it's a ceramic cap it's likely not. Farads are like you said, a measure of capacitance.. It pretty much means for how long it can sustain that charge, sorta akin to the mAh rating on a battery, only farads are based off an absolute charge in coulombs, and mAh is a given discharge over time.. But yeah, for more info on capacitors, read an encyclopedia or something

For a potentiometer, it doesn't really matter what rating it is, since it's adjustable after all, yet the higher the value the pot is the less fine tuning you'll be able to do... For the driver, the lower the resistance, the higher the current... If you use, say, a 10kohm pot, you'll be able to fine tune it really well between 1-10mA, but once you get into higher currents, such a tiny turn on the pot will cause a huge difference in current. I'd suggest using a 25ohm or 50ohm pot, preferably one with multiple turns, to give you some fine tuning ability.

As for a switch, put it between the batteries and the driver, don't put it between the driver and laser diode or bad things happen. Basically, hook up the - end of the battery to the - end of the driver, and have the + end of the battery go through the switch to the + end of the driver.

what happens

 

[pseudolobster]

what happens

There's a capacitor on the output, and if you leave the driver running without a load the capacitor will charge up to it's max voltage (prolly like 16v or 25v), so when you push the button that full charge will go to the diode, killing it.

 

[jamilm9]

ok thanks

 

[bhank]

Wow thanks guys. That really helped me out a lot and cleared up a lot of things for me. Again, thanks.

 

[Benm]

There's a capacitor on the output, and if you leave the driver running without a load the capacitor will charge up to it's max voltage (prolly like 16v or 25v), so when you push the button that full charge will go to the diode, killing it.

The capacitor will not charge to ITS maximum voltage. That voltage is how much the capacitor can handle before it will fail. It will however charge up to the battery voltage, which is often enough to give the diode a deadly jolt anyways.

 

[Things]

The simple LM317 drivers/rkcstr drivers DO NOT limit the voltage, only current, so the capacitor, like Benm said, would charge up to your battery voltage, then dump it into the diode if you reconnected it.

 

[lasersbee]

Yeah... and if it's an unloaded FlexDrive Boost Driver the output voltage will
go much higher than the battery voltage..
Without a load the FlexDrive will increase the output voltage until is senses the
current it was adjusted for... It will try to increase this voltage until it also blows..

Either way... this is an extremely easy way to blow your Laser Diode..:cryyy:

Jerry

 

[LarryDFW]

Blaine;

Welcome to the board.

Since you are in Bedford, you need to drop by this place, instead of Radio Shack.

It is a well-stocked electronics store:

http://www.tannerelectronics.com/

I also have a LM317 circuit drawn, showing the correct switch location on the link below.

LarryDFW

 

[bhank]

I'm sorry LarryDFW but which link is that diagram in?

 

[bhank]

Ok I've got one more question. Will a regular 9v battery work for my Blu-ray or should I use something more stable?

 

[Asherz]

A regular 9V battery will work perfectly with a rckstr driver and PHR-803T blu-ray diode, I believe the minimal amount of voltage required for that combination is 7.2V so 9V it's perfect.

If it's a flex drive on the otherhand, to use a 9V I believe you have to set it up slightly differently on the PCB (I may be wrong there but that's what I remember reading) because it's a boost driver it will run happily on two AA batteries.

hope this helps a little. Oh and just a quick mention but I imagine you know this already, do not what ever you do hook the battery straight to the diode it will own it :L

Good luck.

 

[Bionic-Badger]

The Flexdrive is a boost circuit, meaning it takes can take a lower voltage and produce a higher voltage from it. In fact, it is bad to have the Flexdrive at a voltage greater than about 5.5V, which means you should put some rectifier diodes in series with the batteries to drop the voltage if it could potentially go above 5.5V.

The Rkcstr driver and the LM317-derived drivers require an input voltage above the voltage required for the diode. For the Rkcstr driver, it's like 1-2V, for the LM317, it's around 3V I believe.

So make sure you know which driver you're using so you know how many volts to give it.

Oh yeah, and take Larry's advice about the electronics shop. Radioshack should be the last place you shop for parts. They're overpriced, often have poor quality equipment, and they qualify more as a computer shop than electronics shop these days.

 

[bhank]

Actually I'm using rog8811's driver on his site. Will that still be ok?