TPA6120 Hifi headphone amplifier. 2012-10-12

The objective was to build a hifi headphone amplifier for myself and to CAD a pcb using SMD components. 

The choice for headphone driver circuit fell on the very popular circuit TPA6120 from TI. This is more or less a OP designed for Hifi. A input buffer stage is needed for the driver and for this LME49740 (also Hifi) was chosen.   

The power supply is a double 12Vdc with rated current around 400mA.In the design there are some additional filters and capacitors for reducing noise.Both OP stages are configured with gain=1, for better schematics picture pls email me.

Fuel Gard. 2012-02-20

Is a extension module to be used together with any alarm system on the market that has external input possibility.

The module monitors the level in a tank to avoid theft, for instance diesel. If the fluid level decreases in the tank the module will send an enable signal to the alarm.

Most preferable is to use the module together with a silent GSM alarm that will notify that theft is ongoing.

The module has proven to stop ongoing theft . It uses aWEMA S3 level sensor or any other sensor with the same specifications.

Powerbox 3000 repair. 2012-01-20

I recieved an older Powerbox 3000 that wasn't working well. When i loaded the output with the maximum allowed current (2A), it had a terrible voltage ripple. The picture below show the actual output ripple was around 5V.

Opening the case revealed that all of the electrolytic capacitors were really old and probably dry.  Using my homemade ESR meter showed that basically all capacitors were bad with ESR values at almost 10ohm.It should be 1-2ohms for a standard "low quality" cap!