0.4v -4.98v to 4.98v -0.5v

[wizpic]

Hi all,
I have a couple of these paddle joystick JC120-0002. It’s an Hall effect joystick that gives A voltage output of 2.50v in centre then down to 0.5v backwards and up to 4.98v pushed forwards from the wiper part and a switch type of thing (were you can use it to give direction of lever is pushed). Which is great but I have an application where I can’t use the switch for direction operation and rather than using 2 of them.

Is there a way of creating a second analog voltage where I still get 2.50v in centre and when I push it forward side 1 voltage will increase to 4.98v and side 2 voltage drops to 0.5v and then pull it backwards side one drops to 0.5v then side 2 increases to 4.98v .

 

[danadakk]

Use an OpAmp to do scaling and then another to invert.

Design help -

https://www.ti.com/lit/ml/sloa030a/sloa030a.pdf?ts=1679744291491&ref_url=https%253A%252F%252Fwww.google.com%252F

https://www.mouser.com/pdfDocs/analogengineer%E2%80%99scircuitcookbookopamps.pdf

Regards, Dana.

 

[crutschow]

Here's the LTspice simulation of a single op amp circuit that basically does the offset and inversion you want, but since the input swing is not completely symmetrical around 2.5V, then if 2.5V remains the center voltage, the inverted output swing will be from 0.02V to 4.5V (yellow trace) for an input of 0.5V to 4.98V (green trace).
I suspect that will not be a significant problem in your application.

Note that for a single supply voltage (minimum 5V), the op amp must be a rail-rail type, similar to that shown (definitely not a 741).
All resistors are 1% tolerance or better.

 

[KlausST]

Hi,

Yes, unclear where this unsymmetry in the joystick signal is coming from.
In values:
* center is 2.5V.
* most low is 0.5V, which is 2.0V from the center
* most high is 4.98V which is 2.48V from center.
The 2.0V vs 2.48V is the problem a simple Opamp circuit can not accomplish.

So now it's on the OP to decide what to do.
* leave it as is, then 0.5V --> 4.5V, 2.5V --> 2.5V, 4.98V --> 0.02V (with a suitable RR out Opamp)
* adjust the center to (0.5 + 4.98)/2 = 2.79V, to make 0.5V --> 4.98V, 4.98V --> 0.5V, ... but 2.5V --> 2.21V
* or a more advance solution to "switch between two different gain" maybe with the use of a comparator and an analog switch.

Klaus

 

[wizpic]

Thanks guys,
The other system uses a similar type but this only has 4 wires 2 are the power supply of 12v feed both of the other wires give 2.5v out while in centre then when you push it forwards one increase’s to 4.98v and other decreases 0.5v, there is no markings or can’t find any data sheet for it only a supplier part number which does not relate anything about it.

But that has given me some food for thoughts.