need help about relay!! - Page 2 - Electronic Circuits Projects Diagrams Free

Hero999 · 18th August 2007, 12:59 PM

Doesn't it clamp it to 0.7V below the supply not 0.7V above the supply?

Some of the biggest shocks I've had have been from playing around with transformers and large contactors. The moment you disconnect the battery from the relay the same current will cary on flowing, for an instant, and if you're in that current path it isn't nice. Currents above 5mA are considered harmful and can potentially kill you, however in practice when you interrupt the 20mA goint through a relay it only passed through you for a split second so it isn't too bad. but a big contactor with a current of 2A is a different story.

ericgibbs · 18th August 2007, 03:43 PM

Quote:

Originally Posted by Hero999

Doesn't it clamp it to 0.7V below the supply not 0.7V above the supply?

Some of the biggest shocks I've had have been from playing around with transformers and large contactors. The moment you disconnect the battery from the relay the same current will cary on flowing, for an instant, and if you're in that current path it isn't nice. Currents above 5mA are considered harmful and can potentially kill you, however in practice when you interrupt the 20mA goint through a relay it only passed through you for a split second so it isn't too bad. but a big contactor with a current of 2A is a different story.

hi hero,
The 'spike' at the collector is postive going, wrt Vcc line, so it forward biases the clamp diode into conduction, thats why its clamped to Vcc + the Vdiode fwd drop.

Eriv

Hero999 · 18th August 2007, 04:19 PM

Yes, I agree, the collector is lifted above the supply voltage by 0.7V, I was incorrect.

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18th August 2007, 12:59 PM	(permalink)
Hero999	Doesn't it clamp it to 0.7V below the supply not 0.7V above the supply? Some of the biggest shocks I've had have been from playing around with transformers and large contactors. The moment you disconnect the battery from the relay the same current will cary on flowing, for an instant, and if you're in that current path it isn't nice. Currents above 5mA are considered harmful and can potentially kill you, however in practice when you interrupt the 20mA goint through a relay it only passed through you for a split second so it isn't too bad. but a big contactor with a current of 2A is a different story. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.

18th August 2007, 04:19 PM	(permalink)
Hero999	Yes, I agree, the collector is lifted above the supply voltage by 0.7V, I was incorrect. __________________ I also post at the following sites: http://www.stop-microsoft.org http://www.heated-debates.com Screen name: Aloone_Jonez And http://www.silicontronics.com, same screen name as here.