Manually adjust output voltage?

Status
Not open for further replies.
S

sam_boytor

New Member
I am looking to manually adjust an output voltage to a get specific voltage. For example: the output voltage needs to be 2.5 VDC and my output may be 2.3 VDC or 2.8 VDC. I am looking for a way to manually adjust the voltage using a potentiometer (and possibly some op-amps). Any suggestions?
 
Hi there,


Are you saying that your output *now* runs from 2.3 to 2.8, and you want
it to be a constant 2.5v at all times intead?
 
crutschow - the output is going to a microcontroller so the current requirements are in the mA range.

MrAl - the output will be constant, but for each circuit I make the voltage may be above or below what I want it to be (2.5VDC).

CCD - the classic LM317 voltage regulator can bring my voltage down to what I want, but if my starting voltage is too low I need to increase it somehow.
 
What you are trying to do doesn't make a lot of sense. Could you elaborate on where this output voltage is coming from?
 
The output is coming from an accelerometer. The Accel is on a circuit board which is on a table. When the table is level, the Accel should output 2.5 VDC to the microcontroller. But circuit board doesn't sit level on the table, so I want to be able to adjust a Potentiometer to tell the microcontroller that the table is level.
 

Can you modify the software? Just push a button that tells the uc that the current reading represents "level".
 
Here's an op amp circuit which should allow you to add an offset voltage to your signal.
 

Attachments

  • voltage adder.png
    2 KB · Views: 329
Last edited:
pc88 said:
Here's an op amp circuit which should allow you to add an offset voltage to your signal.
Click to expand...
sam_boytor needs both plus and minus offset adjustment. For that you would need to connect the bottom of the R3 pot to a minus voltage.
 
crutschow said:
sam_boytor needs both plus and minus offset adjustment. For that you would need to connect the bottom of the R3 pot to a minus voltage.
Click to expand...

You're right. Alternatively, you could connect the ground of the ground leg of R2 to Vcc/2 (buffered by a voltage follower).

I think the key issue is which op-amp to use. You'll definitely want a rail-to-rail op-amp that can work with your supply voltage (likely 5V). Add the requirement that you want a through-hole component, and that narrows down the field quite a bit. I'd check out what National has to offer (like the LM6142) as well as Microchip.
 

Attachments

  • voltage adder.png
    2.8 KB · Views: 148
Last edited:
Status
Not open for further replies.

Similar threads

N
  • Question
LM338 gives output voltage input
Replies
8
Views
2K
Tony Stewart
M
  • Question
Low noise TEC driver design - adjustable linear voltage regulator
2
Replies
26
Views
6K
Tony Stewart
S
  • Question
Linear voltage regulator?
Replies
8
Views
2K
Papabravo
B
  • Question
Transformer Power Output Mystery
Replies
12
Views
3K
briesmith
B
  • Question
Project help request: Striking a bell manually, alarm clock.
Replies
12
Views
4K
stevef22
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…