What is this thing?
A circuit board meant to replace the one that comes in the play stove of your Ikea Duktig Mini-kitchen that extends its battery life to many years. This a big improvement from the board that comes with the kitchen, which, due to bad design, consumes batteries in just a few weeks -- even when no one is using the toy.
Can I buy one?
Yes! I initially created just three of them for a couple friends, but so many other people started asking that I produced more and began selling them.
- If you're in the United States, you can buy the board on Amazon. If you have Amazon Prime, two-day shipping is free!
- If you're outside the United States, you can buy the board from my eBay Store; eBay will export it using their Global Shipping Program.
Why did you build it?
My good friend Ben wrote to me one day. He had a problem: his kids love the Ikea Duktig Mini-kitchen. But its light-up play stove takes 6 batteries which seemed to drain every week or two. He'd tried using rechargeable batteries, but that just made the situation worse: they'd barely last a day. Ben knew I liked to tinker with electronics so asked me: could I fix it?
He mailed me the stove out of the Ikea kitchen. I started to tinker with the circuit board inside that controls the burners, and found it had two problems. First, and worst, the board was always drawing at least 3mA (three thousandths of an amp), even when the toy is off. This may not sound like a lot, but with typical 2700mAH AA batteries, the battery energy would be completely drained in less than 40 days.
Second, the LEDs were unregulated -- there was a simple current clamping resistor between the 9v supply and the LEDs, a configuration that only works correctly when the supply voltage is quite close to 9v. This is only true with fresh alkaline batteries. The situation is even more precarious with rechargeable AAs, which are only about 1.25v each when fresh (versus 1.5v for alkaline). I measured the forward diode drop of the LEDs at about 5.8v, and the LEDs need around 15mA to be visible. Ikea's clamping resistor was 110 ohms, so the supply voltage needs to be at least 7.45 volts for the LEDs to work.
Now, Ben's problem had become clear. His stove was starting at 7.5v with his rechargeable batteries (1.25v per battery in series times 6 batteries), and the board's cheap design meant that as soon as the batteries sagged by just five-hundredths of a volt, it would stop working. Because the board was drawing 3mA even when it was off guaranteed the lights would fail almost immediately with rechargeable batteries. Even alkaline batteries would be dead within a few weeks.
I created a new circuit board that fixes all these problems. First, it uses an LED driver as a constant-current source rather than a clamping resistor; this means the board will work over a wide range of battery voltages, even when the batteries start to run down. Second, I carefully designed the board to have very small idle power -- a few microamps. In other words, my board's idle power consumption is about one one-thousandth of Ikea's original board. There's a small microcontroller on my board that shuts itself completely off when the toy is not in use. The only significant idle power draw comes from the voltage regulator's leakage; without that, I measured the idle power draw at 40 nano-amps!
How do I install it?
It's a snap! I designed the board to be virtually identical to the original: it has the same physical dimensions, the same connectors, and mounting holes in the same places. All you have to do is disconnect the wires from the old board and plug them into the new one.
More detailed installation instructions are below.
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This is what your new battery saver board
looks like. There's a similar circuit board inside your
Duktig Stove. We'll be replacing it with this one.
The prototype board pictured in this tutorial is purple, but yours is green. (They are functionally identical.) |
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Here's your Duktig Stove. The hardest part is taking the plastic cover off and getting it back on. It's held in place by 8 plastic tabs (two on each side). |
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First, pull outward on the center of the long edges of the stove frame. With any luck, the top and bottom tabs should release as the plastic cover bows up slightly. If this doesn't happen, get a flathead screwdriver and carefully free the tabs as you're pulling outward on the frame. |
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Carefully push in on the short edges of the plastic cover while pulling up on the center, further bowing the cover upwards until you can release one of the short edges. Remove the cover. |
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Under the cover you'll find the old circuit board we're
replacing. Grab a Phillips head screwdriver and
remove the two screws holding the circuit board into the
stove's frame.
For easiest installation, use a #2 Phillips screw driver for the battery compartment screw and a #1 Phillips screw driver for the circuit board screws, though you can get away with using a #1 or #2 for both purposes. (A #1 Phillips screw driver is usually included (along with a #0) as part of a "precision" or "jeweler's" screw driver set, e.g. Stanley 66-039 or 66-052). |
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Disconnect the five cables that connect to the old circuit board. It may require some force. |
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Connect the buttons' cables to the bottom connectors on the new board. Connect the left button to the left connector, and the right button to the right connector. Note: The old board crosses the left button to the right connector and vice-versa. Uncross them when attaching the new board. |
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Connect the remaining cables: the LEDs running from the "burners" and the power cable running to the battery box. |
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Insert new batteries: the ones you had in the stove previously are probably dead. The old board eats batteries, even when the stove is off. |
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Test the board -- make sure each button turns on
the correct burner. If not, swap the two button cables
on the bottom side of the board. If you see the
little power LED go on, but not the burners, make sure
the burner cables are secure.
If you see no activity at all, make sure all six batteries are inserted in the correct direction and the battery cable is secure. Make sure you're using new batteries; the batteries that were in the stove before are almost certainly dead. |
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If everything works, replace the two screws that secure the control board to the bottom of the stove's frame. |
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Get ready to replace the cover. Make sure the side with the thinner circle goes up. The cover is almost, but not quite, symmetrical. If you try to put it on upside-down, it will almost, but not quite, fit. |
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Put one of the short ends in first. Bow the cover slightly and put the other short end in. Then pull the frame apart slightly to let the long-side tabs slip back into place. |
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You're all done! You'll most likely never have to change your stove's batteries again. Enjoy! |