Introduction: Reviving an AutoDarkening Welding Helmet

About: Engineer. HW/SW development tools.

Reviving an AutoDarkening Welding Helmet:
As an Instructables virgin, I decided to get started with sharing my experience with my Harbor Freight Auto-Darkening Helmet resurrection.

I use my mig welder all the time for quick fabrication of brackets etc. One day
I went out the the shop, fired up the welder, and donned my welding helmet. I then proceeded to start the weld and was surprised by the flash intensity. My auto-darkening helmet had always stepped in and attenuated the bright welding arc, but this time it didn't.

My quick test then was to go outside with the helmet, look at the sun indirectly through the welding lens, while waving my hand in front of lens to create a variation in light hitting the front and sure enough, the lens darkened, but faded back to clear in a second or two.

Items required:

- A welding helmet that needs fixing of this sort.

- A dremel tool with arbor and abrasive cutting disks( or diamond wheel types )

- Hot Glue gun and glue sticks

- A soldering iron and solder

- 4AAA or 4AA batteries.

- Qty2 2-Cell holders( =3VDC ) for the batteries selected above.

Step 1: Finding and Exposing the Battery

On the front of the lens casing, at the top, there appears to be a solar cell.

Over the years I had assumed naively that the helmet recharged over time with ambient light. (Edit: as member::DerStu pointed out, It turns out it does trickle charge if left out in sunlight.)

From experimentation I found that there are 2 additional photo sensors( either photodiode or phototransistor based ) that sense and maintain the darkened state of the lens.

I decided then that there must be a battery or storage super-capacitor inside the lens that had died. Since the lens's plastic casing is approximately 3/8" thick, I guessed that it must use a coin cell type and looked for a reasonable location where they could have placed one.

I broke out my trusty dremel with my favorite attachment: A wheel arbor with a thin abrasive disk. This combination is very useful for all kings of fabrication and dissection of things. (Tip: look up images of "Riemann Sum" and you get the idea of one grinding technique to approximate shapes )

As seen in the picture, I was lucky to find a coin battery on the first try. Using the dremel tool with a pinky finger or two for support on the table, cut out a shallow ( at estimated plastic depth ) square shape approximately postage stamp-sized. Keep the square cutout piece of plastic to use later. The battery should be exposed. At this point make sure you identify and record the battery lead locations and polarity.

Take a small thin bladed screwdriver or precision nippers, carefully, as close to the battery 'weld's, pry the battery tabs upward to break them loose from the battery. Do not put so much stress on them that you break the tab leads at the location where they connect to the PCB. The underside of the battery is harder to work loose, but with patience and control the coin cell battery will cut loose.

Now go out and get qty:2 2xAA or 2xAAA battery holders and qty:4 AA batteries from RadioShack or similar. The emphasis on qty:2 of these holders will be explained later.

Step 2: Adding the External Batteries

Next solder the 2xAA battery holder leads. Red lead to the positive marked lead where the CR3023 battery was connected.

Then do the same procedure with the Black lead to the minus(gnd) marked lead where the CR3023 battery was connected. Cut a slot in the LCD case so that the holder leads can be routed outside the case. Hot glue the wire leads, slot, and glue cutout cover plastic you saved back into place. To break the suspense, I thought I was done at this point, but after tossing in batteries and welding, I found that the darkening attenuation at the dark-most setting of the lens was not what it used to be.

Short_tangent_rant: At this point I got on the internet and did a search to see if anyone else had tried this. I like to reason out and try things first before resorting to Google. This way I have to use my own creative muscles first, before using another person's brain power. This can be both good and bad in that often you can learn from others trial and error before doing a task, but if you always resort to others to tell you how to do things, you don't work through the "eureka" discovery process that can often lead to new and novel ways of doing things. End_Of Short_tangent_rant.

I found some links where people had found a 2nd battery on opposite side of the lens, but they couldn't explain its purpose or why it usually still had reasonable life in the battery. I can clear this up. The first battery powers the analog circuitry( op-amps etc ) that process the light levels an then control the drive to the LCD of the lens that darkens. The 2nd battery is the contrast voltage for the LCD and is responsible for how dark the lens can go. Contrast voltage to LCDs are extremely low current draw so this battery is often still usable.

Contrast voltages are sometimes negative with respect to the other circuitry and this is the case here. The two coin batteries are wired in series, with the first battery's negative connecting through the PCB to the 2nd battery's positive. This creates a bipolar supply +3vdc/-3vdc for both the analog processing and contrast circuits.

So after dremeling the case to expose and remove the 2nd battery, using the same procedure as the first battery revamp, I put in the 2nd set of AA's into the 2nd holder and mounted them inside the helmet above the lens.

I recommend to use Velcro with really good adhesive that wont slide off over time. Liquid Nails item called "Perfect Glue" in a tube is one of the best clear adhesives around. It's not Vinyl bases, but like stiffer silicone on steroids. I used coated Romex wire in a pinch to wrap them in place.

Step 3: Conclusion and Test:

Using the "sun" test mentioned above, I found the helmet worked perfectly and has been in use
for 2 years now without issue.

Good luck, Be Safe, and Have fun Hack-Making

-Lee Studley 20141210 Merry Christmas and holidays to all

I'd like to thank author: HollyMann and others for their inspiring Instructables and creative sharing.

Disclaimer: This instructable involves the use of power hand-tools, electricity, and soldering. If you are not comfortable using these items, then refrain from doing so. I'm not responsible for what and how do after reading this instructable. If you disagree with this instructable or any items therein, please feel free write an instructable reflecting your experiences.