DC

V+ , Vin , Vref all = 12v+
V- = GND

Vin = 0-5v

I'd like the circuit to go HIGH @ Vin > 2.5v and LOW @ Vin < 2.15v

How do I complete the circuit to use Vout on a NPN that grounds a coil leg of a rely (60.4 Ohm across coil)?
And what would be the resistor values needed. And needed diodes?

I'm trying to use one LM358

Thanks,
Rey

 

Assuming the circuit works

Connect 1K resistor from Vout to base of NPN.
Connect 10K from base of NPN to Ground.
Connect Emmiter to ground
Connector coil to collector.
Leave the other leg of coil to Supply Vcc.
Connect a 1N4007 Diode across the coil, the anode side of diode goes to the collector of the NPN. The cathode will go to Vcc.

Now I dunno Ur Vcc Value and what the heck the coil is or does, so I cannot comment on it, the rest is the how to drive a transistor that coils switch anything from a relay to a Motor with the correct Supply Voltage

 

Hi elRey,

The output of the LM358 cannot drive all the way to -V (GND). Therefore the inverter output will always be the same, a few 100mV above GND.

Change the design of the inverter to avoid this problem. Post your updated schematic when done.

Is this homework, or a project? What is the relay voltage rating?

Regards,
Ifixit

 

Thanks for the replies. This is a hobby project. It's 12V DC relay. I've prototyped the schmitt trigger and have it working and controlling a NPN.

And you're right, the inverting amp did not do what I wanted.

So, how can I invert the .6v-9.6v square output of the schmitt to drive a NPN?

I have the top signal, I want the bottom signal to drive a NPN:

And I'd like to be able to do it with the other side of the lm358 or lm393.

Can it be done with a op-amp or comparator? If it can, give me a little while to try and figure it out.

Thanks again,
Rey

 

Simply use PNP + LED to drive the NPN

 

A 555 makes a decent inverting Schmitt Trigger, and can drive a transistor nicely (that drives a relay).

555 Schmitt Trigger

Don't know if it is close enough to what you are after, but there it is.