Simple, no-math transformer snubber using Quasimodo test-jig

[Terry Given]

Mark,

thats a lovely circuit. i like it, and will have a tech build me one so i can give it to the engineers at work who are allergic to analysis.

 

[merlin el mago]

Using 15VDC to supply Quasimodo, attached infinityR

 

[merlin el mago]

Attached 1000R

 

[merlin el mago]

Attached 500R

 

[merlin el mago]

Attached 250R

 

[merlin el mago]

Attached 100R

 

[trobbins]

Merlin, any chance of doing a comparison oscilloscope snapshot of say 250ohm snubber again, but this time with a 50 ohm loading on primary winding (rather than short circuit) ?
Ciao, Tim

 

[merlin el mago]

Primary 50R + 250R

 

[merlin el mago]

Mark when Quasimodo operates the LED is intermittent (shine & not shine) but when operates certain time the LED don't shine?

 

[Mark Johnson]

... when Quasimodo operates the LED is intermittent shine & not shine but when operates certain time the LED don't shine ...

Your Quasimodo v.4 is broken. Here is the relevant portion of its schematic; D2 is the LED. D1 and D3 are protection diodes which prevent overcurrent if someone connects the power supply backwards.

As you can see, there is a pure DC current path (red arrows) from PWR_IN to GND which flows through the LED. The path is

• P1 (external I/O pin) receives PWR_IN from power supply
• D1 Anode
• D1 Cathode (node name: VCC)
• LED Anode (node name: VCC)
• LED Cathode
• 820 ohm resistor R1
• GND
• P3 (external I/O pin) receives GND from power supply

A pure DC current flows through the LED, its value is (Vsupply - (VD1 + VLED)) / 820 ohms . When you drive a standard LED with a pure DC current, it emits a continuous beam of light of constant, non-varying illumination.

 

[merlin el mago]

Any suggestion where to start to check the parts?

 

[AndrewT]

measure the voltage at the resistor and at the LED.

 

[merlin el mago]

Andrew the voltage across the LED & the resistor is jumping

 

[AndrewT]

Measure the power voltage.

 

[merlin el mago]

Used this LED:
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[merlin el mago]

Measure the power voltage.

The bench PSU 15VDC

 

[AndrewT]

The faulty connection is between the PSU and the LED.

 

[merlin el mago]

All diodes are OK

 

[Mark Johnson]

Have you read the datasheet? Carefully search for the word near the green and black arrowhead . . . . .

_

 

[merlin el mago]

I'll check timer, FET & Mosfet.