# This is a picture from a circuit simulator i need help

Discussion in 'Electronics Resources' started by mikelynch, Aug 6, 2014.

1. ### mikelynch Thread Starter Member

Jun 30, 2007
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0
I asked how could I get 6.6 volts from a microcontroller whose pins only put out 3.3 volts.

Well please know I am a real beginner. I downloaded LTSpice and ran this program that was sent to me(the attachment) suggested.

Im not sure what is going on, hovering over the parts and getting the little information that shows up isnt really helping.

Has he used two pins (the 3.3volt pins of the microcontroller) where is the ground ? Is this demonstrating a 6.6volt output ?

The whole reason for my question is I wanted to drive a sensor that needed 6 volts rto work and I wanted to do it via the 3.3volt pins.

Could you explain what is actually going on in this diagram and talk to me like I'm a 7 year old

Last edited: Aug 6, 2014
2. ### MrChips Moderator

Oct 2, 2009
14,499
4,268
Check out the AAC lessons found on the tabs at the top of this page, Volume III, Chapter 3 - Voltage Multipliers

In your case, V1 is fixed +3.3V. V2 is a square wave signal, 0-3.3V.

Because of D1, the node at C1, D1, D2 does not fall below 3V.
When V2 is raised to 3.3V, the voltage at the node is raised to 6V,
D2 conducts to charge C2 to about 5.4V.

Last edited: Aug 6, 2014
3. ### MikeML AAC Fanatic!

Oct 2, 2009
5,451
1,071
There is a problem with the posted LTSpice circuit that prevents it from doing anything...

What is the exact voltage that your sensor needs to operate?
How much current does it require to operate?

4. ### mikelynch Thread Starter Member

Jun 30, 2007
23
0
Sorry about the colour, I never use them but since they are here well There are a couple of ways to drive the motor controller I am using. I've used the same power source that the motor controller uses to drive the wheels but you can power it via a separate 5volt input. I thought maybe connecting two of my microchips 3.3 volt I/o pins could be another way. but the way I connected them I still got only 3.3 volts , so ive a lot to learn about ohms law and series/parallel that is where somebody gave me that LTSpice diagram as a solution. I got very little response from that forum other than to start playing around with components on breadboards and start learning. They have a point and I'm going to do that and it will proably stick, but I've a bit of reading to do to first know how these components operate. But I am still interested in solving this problem now if possible ? even if I get 6.6 volts input I think it won't harm anything, so if you can I'm all ears.

5. ### MikeML AAC Fanatic!

Oct 2, 2009
5,451
1,071
Let me get this... You are trying to get enough current out of the voltage doubler driven from an micro-controller port pin to run a couple of robot motors????

The port pin can typically only source or sink ~25mA, which is too low by a factor of 100 to run your motors, so it is never going to happen...

Let me ask you, where does the 3.3V that runs your micro-controller come from? Chances are that it is coming from a Wall-Wart or a battery pack whose voltage is much more than 3.3V. Why dont you just get a 5V regulator to put between the power source and the motor controller board?

6. ### mikelynch Thread Starter Member

Jun 30, 2007
23
0
That was really an example I thought up. I have the motors running and wont be changing the way its done. But its not to drive the motors actually. They are driven by 4AA batteries. There are also 3 pins on that motor controller that can be used to drive 5volt devices. The microcontroller can be driven by 5 volts. That's what will likely happen in the next phase of building. I think I might be mistaken when I said that the motor controller could be operated via a 5volt input? However im still very keen to know how to get two of the 3.3 pins to output 5 or 6 volts. I think one pin can output 32miliamps but the more pins you use this current drops per pin. There was an example I read of using a 7404 5volt gate with the microcontrollers pins. So I wanted to get two pins to output 5 volts or more rather than use a gate. I understand there may not be enough current to do much. Its more just that I want to get as many volts from the two pins for the sake of theory or learning even if I cant drive a particular sensor. and also to learn to read if not use LTSice diagrams as well .

7. ### Alec_t AAC Fanatic!

Sep 17, 2013
7,095
1,478
MrChips has explained the circuit operation in post #2. Here's the LTspice output from a Transient analysis, which may help you. V1 is the micro's 3.3V supply. V2 represents the voltage obtainable from a pulsed pin of the micro. The V(out) is what should be possible under no-load conditions.

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