IKEA JANSJO Lamp Dimmer

The IKEA JANSJO lamp is a spot light. This project lets you dim the lamp and create a separate power adapter.

1. IKEA JANSJO Lamp (with DIN connector, bar and pin)
2. USB DC variable transformer
3. USB power supply (standard, type-A female)
4. Plastic 3d printed case
5. USB type-A extension cable or standard USB micro cable
6. Female DIN Plug adapter
7. Resistors (see Step 3 for what ones)

Buy assembled

If the metal pins are loose, super-glue them to the plastic. Bend the pins of the DIN connector so they are horizontal and fit into the screw terminals of the DC variable transformer. The rectangle goes on the negative-ground side. Tighten screw terminals.

Find whether your lamp is 4v, 7v, or 21v. It says on the power adapter if you have it. The voltage may also be on the lamp label. You may be able to look up the IKEA model number.

If the voltage is unknown, do the following test to find it:

1. Unplug the lamp if it's plugged into the variable power supply
2. Turn the knob of the power adapter to 4v. Plug in the lamp. Flip the lamp switch. If it lights up, you have a 4v.
3. Turn the voltage to 7v and toggle the lamp switch. If it lights you have a 7v.
4. Turn the knob to 21v and toggle the lamp switch. If it lights, you have a 21v.
5. If it didn't light, then something is not working.

Position the DC power supply so the back is faces upward. Solder resistors to two pins nearest to the center.

1. 4v: 2920 Ohm (2700 + 220: in series)
2. 7v: 6280 Ohm (5600 + 680: in series)
3. 21v: 76,600 Ohm (100,000 || 330,000: in parallel)

Put heat shrink or tape over of the resistors.

You can use different resistors as long as they add up to the same resistance.

Resistor calculator: https://jansson.us/resistors.html

You can skip the resistors, if you remember to never exceed the lamp voltage

(Caution: exceeding the lamp voltage will destroy the LED).

Put the circuit board into the 3d printed case. It's should fit tightly and doesn't require screws.

Power the dimmer using a standard USB power adapter from either Type-A or micro USB port. Connect the IKEA JANJSO lamp to the round DIN connector. Turn the knob to set lamp brightness. Press the case button (below screen) to toggle the lamp on/off. Hold the button for 3 seconds to toggle the 7-segment screen on/off.