Hello all,
I've been building a device that helps firm up the shifts on my car. I have two controller designs built and assembled on one single Perf Board. They both are working well...
One design is based on the LM3914. The IC is being used a gate controller that closes PNP transistor switches. Each switch then feeds current to a slide POT, which adjusts the current to a Power Transistor...
The other controller design is a simple non-inverting op amp that uses a 10K POT as a variable voltage divider used to manipulate the gain. The output of the op amp feeds current to the Power Transistor.
Both designs are being driven by a .5 to 4.5V signal coming from my accelerator. This signal wire is fed through a 50K resistor that drops the current so low that if I either short the wire to ground, or I back feed 14V to the wire (the two worst case senerios), there is no effect to the car's throttle control at all... The current is way to low. I only mention this to insure the good people here that the signal tap is safe...
All this said... the op amp design is hugely more simple... BUT... The gain is linear... And although it works well. It does not work as well as the gate controller (which has a dedicated adjustment slide per gate).
When I look at ow the slides are adjusted on the gate controller, I would say that it's an increaseing curve...
See attached Thumbnail (red line).... (it's an increasing gain value)
Can something like this be done with an op amp? a no-linear increasing output?
In plain english I want to amplify a .5 to 4.5V signal to a 1V to 12V output, with more of the gain increase in the last half of the span...
Hope this makes sense...
I added a chart that I made up that sort of shows what's going on...
The left axis is Vout @ 400ma. 100 = 12V
The bottom Axis is the gas pedal signal shown as 0 to 100% (.5 to 4.5V)
The red line is what the gate controller is doing...
The blue line is the gain controller (op amp) with a gain = 2
The green line is the gain controller (op amp) with a gain at something > 2
The black line is what I'd like my gain controller to do. (I was thinking to try and introduce a step change somehow...
I'm trying to build on what I already have and not start over...
Here are a couple viedos showing what the device looks like...
All help will be appreciated. I have found a lot on non-linear op mp circuits on the web but I'm having trouble understanding what I'm seeing. I'm VERY GREEN when it comes to all this...
I've been toying with the thought of using zener diodes to manipulate the signal from the gas pedal etc... I decided it's best if I get some input before doing anything more...
Thank You...
---
I've been building a device that helps firm up the shifts on my car. I have two controller designs built and assembled on one single Perf Board. They both are working well...
One design is based on the LM3914. The IC is being used a gate controller that closes PNP transistor switches. Each switch then feeds current to a slide POT, which adjusts the current to a Power Transistor...
The other controller design is a simple non-inverting op amp that uses a 10K POT as a variable voltage divider used to manipulate the gain. The output of the op amp feeds current to the Power Transistor.
Both designs are being driven by a .5 to 4.5V signal coming from my accelerator. This signal wire is fed through a 50K resistor that drops the current so low that if I either short the wire to ground, or I back feed 14V to the wire (the two worst case senerios), there is no effect to the car's throttle control at all... The current is way to low. I only mention this to insure the good people here that the signal tap is safe...
All this said... the op amp design is hugely more simple... BUT... The gain is linear... And although it works well. It does not work as well as the gate controller (which has a dedicated adjustment slide per gate).
When I look at ow the slides are adjusted on the gate controller, I would say that it's an increaseing curve...
See attached Thumbnail (red line).... (it's an increasing gain value)
Can something like this be done with an op amp? a no-linear increasing output?
In plain english I want to amplify a .5 to 4.5V signal to a 1V to 12V output, with more of the gain increase in the last half of the span...
Hope this makes sense...
I added a chart that I made up that sort of shows what's going on...
The left axis is Vout @ 400ma. 100 = 12V
The bottom Axis is the gas pedal signal shown as 0 to 100% (.5 to 4.5V)
The red line is what the gate controller is doing...
The blue line is the gain controller (op amp) with a gain = 2
The green line is the gain controller (op amp) with a gain at something > 2
The black line is what I'd like my gain controller to do. (I was thinking to try and introduce a step change somehow...
I'm trying to build on what I already have and not start over...
Here are a couple viedos showing what the device looks like...
All help will be appreciated. I have found a lot on non-linear op mp circuits on the web but I'm having trouble understanding what I'm seeing. I'm VERY GREEN when it comes to all this...
I've been toying with the thought of using zener diodes to manipulate the signal from the gas pedal etc... I decided it's best if I get some input before doing anything more...
Thank You...
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