9-Volt Transformer?

[Eric Johnson]

I have a nice little Delta drill press that came with a laser, which makes a neat crosshair on the surface being drilled. The only problem is that while the press plugs into the wall, the laser relies on a 9-volt battery for some reason. I've noticed that if you forget to turn the laser off, it will eat a brand new battery up in about 24 hours. I love the laser, but am appalled by the potential for waste. Why couldn't they engineer the laser into the rest of the electronics on the drill press?

I'm wondering if it would be possible to dig up a 9-volt transformer from some long-dead electronic gizmo and power the laser that way. Would it just be a matter of connecting the wires from the transformer to the battery leads and plugging the thing in, or is there more to it than that?

 

[eba1225]

As long as it has a DC output and the output is comparable to a battery you should be right as rain.

 

[Corey]

Well - maybe...

If you find a really cheap "wall wart" transformer, it's DC output may really only be a rectified AC output. I've torn apart plenty of them that only have a transformer and 4 diodes to make a full wave bridge - nothing else! Instead of a full AC sine wave, it would give you a string of pulses - zero to maybe 12V with the average being 9v. It would then rely on additional electronics in the device to smooth and regulate the power to a usable DC approximation. Your battery is about the purest form of DC there is, but your cheap transformer may be putting out pulses that won't be tolerated well by the laser diode.

If you have a 'good' wall wart that has some power regulation, that would be better, a SMPS from an old computer might be a little more bulky, but would give a much better DC supply. Unfortunately, you would almost need an o-scope to see what a wall wart is putting out and decide if it's acceptable.

 

[Eric Johnson]

Maybe a rechargeable 9v battery is a better solution.

 

[Kenny1]

I would just use a regulated 9V adaptor. You can get battery elimator with the snap connections, or just get a regulated adaptor, strip the leads and solder to the battery connection.

I have soldered a 9V adaptor to a spare battery snap to make a battery elimanator in the past (watch the polarity!). Parts can be found at Radio Scrap, or other electronics hobby store.

Cheers


Kenny

 

[Corey]

Maybe a rechargeable 9v battery is a better solution.

That would help - Also, is there any possibility that you could wire it up to a momentary switch. Pull a trigger, do your laser sighting, then when your finger is off the button, the laser goes off. Or, one step up the ladder - a timed switch where you push the button, laser stays on for some convenient time, then automatically shuts off.

 

[eba1225]

eric,

all you need to do is read the label of the transformer,
it will say AC or DC, if not don't take the chance,
also it should show the current rating, you should not need anything more than 250 mA of current (also shown on the label).

 

[Jags]

Eric, Kozy Heat is right on the money when he says that bad DC voltage could hurt your laser. If you are looking for power supplies, you may want to look at the power supplies from older, more expensive equip. such as old lap tops (although most are above 9v) and external modems (most are at 9V AC). I know these 2 examples are of no help, but it may get the mind moving. More sensitive equipment will more than likely have better power supplies.

 

[Gooserider]

Another option is to wire a largish electrolytic cap (say 100 uF, 15V rated) in parallel with the wall wart (Put it across the battery terminals and stuff it into the battery compartment perhaps?) in order to filter out any noise or ripple from the cheapo wall wart...

Gooserider