Odd Question - Convert from 9V Battery to Wall Wart Power Supply?

I’d like to convert my luxmeter (the LX1330B) to be powered by a AC-to-DC wall wart instead of using a 9V battery. I’d like to do this because I want to leave the luxmeter on during runtime testing and such. Has anyone done this? Can I simply find a decent 9V wall wart (guessing rated 500mA or higher is fine) and adapt the ends to the 9V snap connector (keeping polarity correct - I already know it’s going to be backwards from what is expected)? Does the supply need to be well regulated? Thoughts? Or should I stick to a chinese regulator circuit and adjust it to 9.0v? (Though then I have exposed electronics not in a case.) I don’t want to overkill this, but I don’t want to spend much money on this either. If I can avoid much DIY it would be nice (not much time for that anymore).

Thanks,
Garry

I’ve tried it (on a different type of device) and the wall power is not very clean, it introduces distortion and noise. That said this was years ago and perhaps a power brick today would be better or i had a crummy one.

I did a similar conversion on a wall clock that took 2×AA: soldered a short lead to the battery compartment connections, put a barrel socket on the other end and plugged a 3V wall power supply into it.

Worked fine, although you will need a good quality power supply. As Bort says, poor quality power supplies can allow noise from the mains to reach your device. That may be a particular problem for a test instrument where you care about accuracy of measurement.

Mind you, if you do have trouble using a mains power supply, there’s nothing to stop you using a 6×1.5V AA battery carrier to get 9V with more runtime.

You could also go for a rechargeable NiMH-based solution using an 8×AA carrier with 7×1.2V NiMH AA and one dummy cell to get 8.4V nominal.

If you prefer a Li-Ion option, 3×3.7V 18650 and a low dropout (LDO) 9V voltage regulator will get you there. Just make sure your cells don’t get over-discharged; protected cells are a good idea here, as a last-ditch precaution.

You can add a 16V 47uF capacitor to clear the output

Hmm. . . I did read about noise/distortion, but those posts were in regards to powering audio equipment so I didn’t know if that mattered in this case. Is a solution easier if I used something like a 12v SLA battery (I have an old one which probably has enough capacity for what I need) as my source with a 9V cigarette lighter type power adapter?

-Garry

That could work, i like the 6AA solution, use eneloop and your laughing. You can buy the battery holders for cheap
https://www.fasttech.com/products/0/10002604/3945500-6-aa-serial-battery-holder-case

Lexel,
How would that get added? On the DC side in series (on positive wire? or negative wire?)? Or across the AC side (i.e. inside the wall wart power supply)?

-Garry

placing an electrolythe capacitor to line voltage is fun if you like fireworks

parallel to the DC output to eliminate ripple and spikes

I actually have a 6 AA cell holder that has the compatible 9V connectors already on it.
It IS a 9V replacement