Hi,
Learning here.
Would need some help modifying this circuit.
In the circuit below, V2 controls when Q6 conducts:
When V2 is set to a 5V (negative) voltage, you see 12V at Out.
When the output of V2 is changed to 0V, Out is close to 0V.

I would like to change it, so that it can be controlled by a voltage from a processor like an Arduino board:
5V turns Q6 on.
0V turns Q6 off.
Any ideas?

 

Hi chad,
Post your LTSpice asc file and I will modify the circuit.
E

 

If you remove the diode (replace with a piece of wire) and remove R4 (leave disconnected) it should work as you want.

 

Here is the .asc file

 

If you remove the diode (replace with a piece of wire) and remove R4 (leave disconnected) it should work as you want.

That did not work.

 

It worked for me, unless I have misunderstood you:

 

hi chad,
Try this.
E

 

It worked for me, unless I have misunderstood you:

View attachment 313778

Set V1 as a DC Voltage source set to 0V, and look at the output. Does it work for you?

 

hi chad,
Try this.
E
View attachment 313780

Set V1 as a DC Voltage source set to 0V, and check the output.

 

Set V1 as a DC Voltage source set to 0V, and check the output.

I think you misunderstand what is supposed to happen when Q6 turns ON.
When Q6 turns ON, the output at the collector is close to 0V.

 

It worked for me, unless I have misunderstood you:

View attachment 313778

@boostbuck

Did you notice in the OP "V2" is connected opposite of "V1" in your circuit?

 

Ah so!
TS did state 5V (negative) in opening post.

 

The output from an Arduino is not a negative 5 volts.
Some people misinterpret this as a minus voltage moving from +5 volts to zero.
Obviously if V1 is zero then the output is always zero.

 

 

The output from an Arduino is not a negative 5 volts.
Some people misinterpret this as a minus voltage moving from +5 volts to zero.
Obviously if V1 is zero then the output is always zero.

Ah so #2!

 

hi chad.
You asked for this
I would like to change it, so that it can be controlled by a voltage from a processor like an Arduino board:
5V turns Q6 on.
0V turns Q6 off.

That is exactly how my circuit functions in post #7.

How is it wrong???

E

 

Thanks for the responses. To clarify, this is the truth table for the desired circuit:

Base of Q6 Out
-----------------------
______0V __________ 0V
______5V _________12V

I hope it makes sense.

 

hi chad,
How close to 0V must it be, and what is the output driving into?
E

 

You can do it with a two-stage common emitter BJT configuration.
Or you can use an IC such as SN7407 hex buffer or dual peripheral driver SN75451, etc. Note that these have open collector outputs and require a pull-up resistor to +12V.

 

hi chad,
How close to 0V must it be, and what is the output driving into?
E

Hi, if you simulate the original circuit, when V2 is 0V, out is around 11mV, so I would say below 0.5V.