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Very basic and probably dumb question.

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I recently built a laser using the survival lasers black anodized Host, copper extended heat sink, copper pill, 9mm 445nm diode from DTR with his 2.4A driver. Everything worked great at first, but I soon started having issues. I sent it back to DTR and he fixed it for me. He said that I probably put the batteries in backwards and reversed the polarity.

This leads me to my question. How are the batteries supposed to be inserted? I just assumed that the negative end should go toward the spring and the positive toward the battery board. Am I doing it backwards? Any help would be appreciated. I don't want to damage it again by putting the batteries in backwards.
 

ChaosLord

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Depends on how you wired it. Generally it is negative to tail cap, especially if you wired the black lead from the module to the negative contact on the contact board.
 
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Depends on how you wired it. Generally it is negative to tail cap, especially if you wired the black lead from the module to the negative contact on the contact board.
I simply wired the negative (black wire) from the diode to the negative (black wire) of the battery board. Same with the positive (red) leads.
 

Shadowsix

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One thing I've started doing on my very expensive laser builds (1W 520, 2W M462, etc. ) is to put in some very simple but effective battery polarity protection using a Schottky diode on one of the power wires leading to the driver.

The Schottky diode only uses typically .3V (has .3V drop across it) but if you put your battery (or batteries) in backwards it will stop voltage from flowing rather than the driver or laser diode burn if it wasn't there.

The diodes are very inexpensive but very effective, I bought a pack of 5 MBR380 Shottkey Diodes on eBay for $6 (including shipping) and you only need to use one in a build. It would take a reverse voltage of 80V at 3A to overpower this diode so my laser is protected very well.

You can put it either on the negative or positive lead coming from the battery contact pill. If you put it on the positive lead then you want the cathode (the side of the diode that has the silver line around the end) towards the driver). Or if you want to put it on the negative lead then you want the cathode towards the battery.

On my Lightsaber build I put one inline on the positive lead with the cathode towards the laser driver as you can see here:



The negative lead from the battery on this host is on the heatsink as you can see in the picture (a case negative build basically).

Below is a closer pic of a diode so you can see the silver cathode line more easily.
 

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One thing I've started doing on my very expensive laser builds (1W 520, 2W M462, etc. ) is to put in some very simple but effective battery polarity protection using a Schottky diode on one of the power wires leading to the driver.

The Schottky diode only uses typically .3V (has .3V drop across it) but if you put your battery (or batteries) in backwards it will stop voltage from flowing rather than the driver or laser diode burn if it wasn't there.

The diodes are very inexpensive but very effective, I bought a pack of 5 MBR380 Shottkey Diodes on eBay for $6 (including shipping) and you only need to use one in a build. It would take a reverse voltage of 80V at 3A to overpower this diode so my laser is protected very well.

You can put it either on the negative or positive lead coming from the battery contact pill. If you put it on the positive lead then you want the cathode (the side of the diode that has the silver line around the end) towards the driver). Or if you want to put it on the negative lead then you want the cathode towards the battery.

On my Lightsaber build I put one inline on the positive lead with the cathode towards the laser driver as you can see here:



The negative lead from the battery on this host is on the heatsink as you can see in the picture (a case negative build basically).

Below is a closer pic of a diode so you can see the silver cathode line more easily.
Shadowsix,

Thank you for the suggestion. I just ordered some 5A 40V Schottky diodes. I could only order them in much larger quantities than I need (40 pcs), but they will be here on Monday. I decided to get the 5A 40V ones because I am running the driver at 2.4A and wanted a little more protection than .6A. I am glad that there is a simple solution to protect against reversing the polarity and saving laser diodes and drivers.
 
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One thing I've started doing on my very expensive laser builds (1W 520, 2W M462, etc. ) is to put in some very simple but effective battery polarity protection using a Schottky diode on one of the power wires leading to the driver.
I was just reading about bridge rectifiers. In theory, at least, it turns out that you can take the single diode idea one step farther and make a small diode bridge. At that point, it doesn't matter which way you insert the battery. You can insert it either way you want and the output polarity will be the same in both cases. As long as the bridge and its output are wired correctly, it shouldn't be possible to toast your driver by putting the battery in wrong. A diode bridge can be made very compactly, so should be able to fit it into a lot of things, even a C6. I think even a klutz like myself could do that.

The only worry I'd have is that some sort of oscillation or noise might be introduced into the driver circuit due to capacitances or whatever involving the diodes. But if that isn't a likely problem, then perhaps reverse polarity can be more or less eliminated as a concern. Thoughts?
 

Shadowsix

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I was just reading about bridge rectifiers. In theory, at least, it turns out that you can take the single diode idea one step farther and make a small diode bridge. At that point, it doesn't matter which way you insert the battery. You can insert it either way you want and the output polarity will be the same in both cases. As long as the bridge and its output are wired correctly, it shouldn't be possible to toast your driver by putting the battery in wrong. A diode bridge can be made very compactly, so should be able to fit it into a lot of things, even a C6. I think even a klutz like myself could do that.

The only worry I'd have is that some sort of oscillation or noise might be introduced into the driver circuit due to capacitances or whatever involving the diodes. But if that isn't a likely problem, then perhaps reverse polarity can be more or less eliminated as a concern. Thoughts?
Yes you can use a bridge rectifier which is primarily used to rectify AC into DC (pulsed without capacitors, smoothed out with caps) but your real problem isn't introducing stray capacities to the driver but the fact that no matter what you are going through two diodes no matter which way the batteries are placed and therefore dealing with twice the voltage drop because of it.

I.E. using Schottky diodes of average .3v drop to build the bridge you would then lose .6v instead (even worse would be to use standard .7v drop diodes which would mean 1.4v drop!). With our low voltage devices .3v can be tolerable, .6 might not be!
 




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