Power Your Soldering Iron With a Drill Battery!

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Introduction: Power Your Soldering Iron With a Drill Battery!

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Back in June of 2017 I moved out of my parent's house and started renting my own. One of the many things that changed was my workspace. I went from a 12' x 13' room to a 4' desk which meant I had to make some changes. One of the major changes was switching from a soldering / hot air rework station to a TS-100 as my main iron. I ended up falling in love with this little thing but I still didn't have a way to make it mobile. That is where this little circuit comes in. I designed this circuit to fit onto a Dewalt 20v Max battery and provide power to my iron, as well as protect the battery and charge my phone.

Step 1: Supplies

I actually ended up making a kit for this project. If you are interested you can buy one here: https://goo.gl/X6EB9e

If you're purchasing the kit it will come with everything you need including instructions and an optional 3d printed case so feel free to stop reading here. (Or continue to see how the rest of us build it)

So now that I got my shameless plug out of the way, let's get started. This Instructable will be forgoing the 5v regulator for charging phones as buck converters can be finicky to work with (especially on breadboards).

These are all of the parts you will need for the battery protection circuit:

2x - Tab connectors for plugging onto the battery https://goo.gl/uUPTNX

1x - 100UF 25V Capacitor https://goo.gl/8ot59d

1x - 2.5x5mm Power jack for plugging your iron in https://goo.gl/EikcyX

1x - 3' Power cable https://goo.gl/6PeuMr

1x - slide switch https://goo.gl/YGuxcZ

1x - 15v Zener diode https://goo.gl/CRdySZ

1x - N-Channel FET https://goo.gl/xW8Nkt

2x - NPN Transistors https://goo.gl/A2ZvhZ

1x - 3mm LED https://goo.gl/yfDEDt

1x - 820 ohm 2w resistor https://goo.gl/zmJm82

1x - 1k 1/4w resistor https://goo.gl/WPUuiu

1x - 1M 1/8w resistor https://goo.gl/gtNNks

2x - 100k 1/8w resistor https://goo.gl/7jejwj

1x - Prototyping Board https://goo.gl/Dz41hF

Step 2: Testing the Circuit

One of the most helpful steps that I like to do before soldering a circuit is breadboarding. This isn't strictly necessary but in my experience setting everything up on a breadboard helps visualize the circuit you're about to build. If you have a breadboard handy, check out the schematic (first photo) and build it up. If you don't have one handy, however, feel free to check out the second and third photos.

Step 3: Soldering the Circuit

Once you have the breadboard built up, It's easy to decide how you want to solder it to the perf-board. Unfortunately, I don't have an example photo as I have been working with printed PCBs but I can offer a few tips that I've found along the way.

1. You are most likely going to have to drill out some of the perf-board holes in order to get the prongs to fit correctly. Keep in mind:

  • The prongs (battery connectors) should be spaced ~22.5mm apart.
  • The prongs are under stress when you plug/unplug the battery... It wouldn't hurt to add a little JB Weld for strength.
  • B+ on the battery is +20v and B- is GND. See 1st Image.
  • Don't mess with the center pins. They are used to balance-charge the battery pack.

2. Static is bad and can cause electronics to do odd things.

  • Keep the main parts of the circuit close together. (ex: Don't run 3' of wire from the zener diode to the first transistor.)
  • If possible, make a case for your circuit. (even just a shield would be good)

3. This is made for soldering irons, not your oven.

  • Don't use this circuit with things that take a ton of power. There is no thermal protection in the Dewalt batteries so an excess of current can heat them up.
  • This isn't a 9v. Don't lick the circuit.

Step 4: How Does This Work?

Congratulations! You now have a perfect little power supply for your TS-100 soldering iron! Now that you built it, how does it work? (This may be slightly technical.)

The voltage from the battery hits the zener diode. If the voltage of the battery is over 15v, the zener breaks down and starts to let electricity through. After about 15.25v, there is enough current to trigger the first transistor. This transistor pulls the second transistor's gate low which turns off the current flow through it. Because there is no connection to ground, the 100k resistor pulls the MOSFET gate high which turns on the power to your iron. (The capacitor is just to smooth out any oscillation when the battery is low.)

I hope you guys enjoyed this Instructable! Make sure to stay safe while soldering. If you liked this idea or have any suggestions, don't forget to leave a comment!

Also, If you want to buy the kit version of this with the 5v USB charger part of the circuit included, make sure to check it out here: https://goo.gl/X6EB9e

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    Would you be willing to do one for the Ryobi lithium 18v batteries.

    Ryobi Batteries have their own regulating circuits so it is safe to use them as they are. I am however working on a simple circuit that will clip onto Ryobi batteries to charge phones and provide power to your iron. Because the circuits will be much more basic they will be much cheaper. (probably $5-$10) I'm just waiting on a friend to lend me one of their batteries for testing and then it will be available on my store.

    13 Comments

    TS-100 with custom firmware can be connected directly to the battery without deep discharge protection as this can be done on the firmware. Of course, you will miss phone charging ability but I guess it's not the primary function of this hack.

    This is true and I have the Ralim firmware installed on my iron. The problem that I ran into is that the firmware is designed with Li-Po batteries in mind so the "5s" cutoff is set at 16.5v instead of the 15v that the DeWalt batteries are designed for. (the circuit that I designed is set at 15.2v just to be safe) You could argue that you're not gaining that much extra runtime by using my circuit instead of the iron's cutoff but I figured that if I was going to make an adapter I might as well make it nice. Plus it is good practice to have cutoff circuits on your batteries which as an added bonus would let you use it as a power source for other uses.

    OK, agree, that some extra juice is always good. I argued a lot with Ralim regarding "Advanced" option to set cut-off voltage by 0.1V - let's see - maybe something good will happen :) By the way, can you share case 3D model?

    Oh yes, I was just reading you guys' debate yesterday. I'm assuming you're talking about the thread where the one guy arguing against an advanced voltage option saying that he doesn't even change the time on his clock for daylight savings... I totally agree with you though, we have a "detailed screen" setting, why not an "advanced voltage" setting? Anyways... The stl files can be downloaded from my Thingiverse here: https://goo.gl/HU1cKT

    Very cool, both in concept and execution. Great idea! Only con I have is that it would have been nice if you'd explained the operation and design choices of the circuit a little more. Still a great instructable.

    Great idea, but I cannot quite match the schematic and parts list with the circuit. For instance: Where is the inductor L1?

    The inductor is for the 5v power supply that is on the kit's circuit board. I talk about it in the introduction.

    sorry ArnieO the post was meant for the author. somehow i cant delet the erroroneous post

    sorry to say this but your design is flawed and is unreliable even for your battery. you should not be selling stuff that does not work. if anybody really wants to use this then ask and i will give you the correct fix for the circuit.

    The DS100 soldering iron will work directly with any drill battery in the range of 12V to 24V. No regulation circuit is required. However, as yrralguthrie has explained, the battery needs to be protected against over discharge. The circuit as described may work but may not be reliable, the zener should not be used in this way. The zener should go to a 10k (or less) resistor to ground. That junction should then go to the transistor base via a 10k-47k resistor.