Project:Traffic Light Button

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Traffic Light Button


The Traffic Light Button is a Siemens "Puffin Combined Unit". This is a Nearsided Unit with a built in Demand Indicator. The part number is 667/1/33604

Powering the lamps

Different sources suggest different "flavours" of AC are required, including full AC, half rectified AC, and fully rectified AC. There are also references to -48V Operation.

In reality it's very forgiving and will run on regular AC or DC with no visible difference. Polarity is not important owing to the Full Bridge Rectifier built into each lamp unit.

When supplied with ~48V the lamps are at full brightness. According to documentation, the lamps will be dimmed when supplied with ~27.5V. In practise anything below 40V seems to dim the lamps. Unless you want to burn out your retinas I suggest operating in dimmed mode for indoor usage.

Note: The LEDs appear to be driven with PWM so full brightness and dimmed operations are stepped. There isn't a linear relationship between voltage and brightness.

Current Requirements

The lamps require the following current when they're all lit:

Volts Total mA Watts
48 DC 429 20.6
32 DC 138 4.4


One of the lamp modules, showing fairly complex circuitry.