adding 2 voltages and subtracting 1

[kinarfi]

I have 3 voltages/signals that I need to combine, I'm using a VCC of 10 and trying to have everything operate around 5, the first input is the controlling signal and has 5 as it's center and the second is the feed back signal and centers on 2.5 by design, I can wire it so feed back is 2.5 + feed back or 2.5 - feed back, then I need to subtract the 2.5 which makes for the 3rd voltage. I've tried to simulate several methods, but just not sure what works most reliably. There are difference amplifiers and inverting and non-inverting summing amplifiers shown in several places, but nothing for adding 2 and subtracting 1.
Any suggestions? I don't have a - voltage that I can add, every thing is above 0. here's what I have, attached

Thanks,
Kinarfi
SORRY for double posting, checking to see which works best
Attached Files:

• 
  Untitled.png
  File size:
  27.3 KB
  Views:
  1
• 2013-11-13 POWER STEERING.asc
  File size:
  18.6 KB
  Views:
  0

 

[Ratchit]

I have 3 voltages/signals that I need to combine, I'm using a VCC of 10 and trying to have everything operate around 5, the first input is the controlling signal and has 5 as it's center and the second is the feed back signal and centers on 2.5 by design, I can wire it so feed back is 2.5 + feed back or 2.5 - feed back, then I need to subtract the 2.5 which makes for the 3rd voltage. I've tried to simulate several methods, but just not sure what works most reliably. There are difference amplifiers and inverting and non-inverting summing amplifiers shown in several places, but nothing for adding 2 and subtracting 1.
Any suggestions? I don't have a - voltage that I can add, every thing is above 0. here's what I have, attached

kinarfi,
You need to look at this link. Ratch
https://electronicdesign.com/ideas-...chit@comcast.net&YM_MID=1428104&sfvc4enews=42

Thanks,
Kinarfi
SORRY for double posting, checking to see which works best
Attached Files:

• View attachment 82124
  Untitled.png
  File size:
  27.3 KB
  Views:
  1
• 2013-11-13 POWER STEERING.asc
  File size:
  18.6 KB
  Views:
  0

 

[alec_t]

the first input is the controlling signal and has 5 as it's center and the second is the feed back signal and centers on 2.5 by design

Surely the feedback signal needs to be comparable in magnitude to the control signal if you are using both signals to regulate something?
BTW you will need an opamp/comparator with rail-to-rail input and output if your control signal can reach near 10V and you want the output signal to be greater than ~8.5V.

 

[kinarfi]

Thank you for your replies, got it solved.
Kinarfi