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From: "Frank Bemelman"
References: <3D7F3B28.CB607B4C@nospam.com> <email@example.com>
Subject: Re: Using The Parts You Have
Date: Wed, 11 Sep 2002 22:05:42 +0200
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Organization: EuroNet Internet
NNTP-Posting-Date: 11 Sep 2002 20:05:51 GMT
"Ed Edmondson" schreef in bericht
> Well, I have the first op amp working (I think). You vary the temperature
> the output switches on and off depending on the pot setting. I took the
> of the first op amp and fed it through a 1000 ohm resistor to the base of
> 2N3906 to turn on an LED. However, I tried to connect the output (in
> to another 2N3906 transistor to actuate a relay to turn on the resistive
> and when connected the output will not turn on either the LED or relay. I
> to connect the second op amp as a voltage follower and I get the same
> The relay is a 5 volt coil version of a DPDT relay. It is evident I am
> something wrong.... but what?
Seems okay, assuming you connected the base to the other base, with these
> The pin 1 output of the first op amp is connected through a 1,000 ohm
> to the base of the 2N3906 and the emitter is connected to the cathode of
> LED through a 330 ohm resistor to plus 5 volts. The collector is connected
> ground. This circuit seems to work fine.
> I tried the follower suggested by this list and connected the output (pin
> the first op amp to minus input (pin 6) of the second op amp and connected
> plus input (pin 5) to ground. I measured the output of the second op amp
> stays at 3.88 volts no matter where the pot is set.
That's not a follower. Connect the output opamp#1 to + input opamp#2.
Connect the output#opamp2 to - input opamp#2.
Output opamp#2 should now behave like output opamp#1.
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