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DSO150 Power Supplies: Bring the Noise!

Finally getting around to measuring the boost converter between the 18650 lithium cell and the DSO150 oscilloscope:

DSO150 - 18650 boost V - input output 100 mA-div

DSO150 – 18650 boost V – input output 100 mA-div

The yellow trace shows the booster output voltage is 9 VDC, as set by the twiddlepot, and doesn’t vary much under load. It has 200 mV ripple at 220 kHz, the booster’s switching frequency, which doesn’t induce any meaningful noise on the scope’s display, because it’s well outside the display bandwidth and well inside the voltage spec.

The current traces are 100 mA/div from Tek Hall effect probes. The green trace is battery current to the booster, varying from 200 to 300 mA, averaging 250 mA. The cyan trace is DSO150 current from the booster, 75 mA min, 200 mA max, averaging 100 mA.

The battery current is 2.5 × the scope current, the battery voltage is 1/2.5 × the scope voltage, and all is right with the world.

Two multi-output wall warts (Powseed and Leapara, for whatever that’s worth) with a bag of right-angle tips just arrived and I gimmicked up a connection directly to the output:

Powseed multi-voltage supply - hack-job test connection

Powseed multi-voltage supply – hack-job test connection

Which went to a 100 Ω dummy load drawing about the same current as the DSO150:

Power supply load test - 100 ohm resistor

Power supply load test – 100 ohm resistor

Both seem to work OK, albeit with plenty of spiky noise:

PowSeed Multi-Voltage Wart - 9 V 100 mA-div

PowSeed Multi-Voltage Wart – 9 V 100 mA-div

Much to my surprise, there’s no visible noise on the DSO150 display, surely because the scope’s bandwidth is nowhere near wide enough to grow that kind of grass.

A power supply like that would convert the DSO150 into a bench instrument suitable for low frequency circuitry.

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