converting 3.2v-0V to 0V-32.V - Page 1
Forum section: electronics / beginners

author: inlanoche
author_rank: Newbie
timestamp: May 02, 2020, 02:18:39 am
content: I have a very basic education in electronics, but enough to follow basic instructions. My brother and I have been working on doing some modifications to his XBox steering wheel rig. So far we have followed instructions to wire out a switch to tie in a hand break to either the A or B buttons. tested and working great. My brother had some old gauges that he wants to now tied to the gas pedal. so we traced on and tested the pedal output. The power gives a constant 3.2V. The signal wire gives out from 3.2V to 0V as the pedal is depressed.So at no pedal, the signal gives 3.2V. When fully depressed it gives off 0V.The gauge uses 0 (at 0) and goes up to 1V (at 'full throttle').As you can see, the gauge would be backwards based on the signal (once we scale it down to 1V to 0V), meaning when the pedal was up, the gauge would go full, and when pressed it would drop to 0... is there a way to use the power and Signal cables to reverse the variable resistance (to get the gauge to go the right way)?I would have googled this specifically, but I don't know the terminology used to describe this. It's not inverting the signal, as I believe that that would result in a negative value output?Thanks.

author: Mp3
author_rank: Frequent Contributor
timestamp: May 02, 2020, 05:41:02 am
content: Quote from: inlanoche on May 02, 2020, 02:18:39 amThis should be the same principle. You can simply change from normally open to normally closed if needed.

author: helius
author_rank: Super Contributor
timestamp: May 02, 2020, 06:45:17 am
content: The gas pedal of a steering controller is probably more like a potentiometer than a switch. But, the principle is similar because both are implemented as three-terminal devices. The switch terminals are Common, Normally Open (NO), and Normally Closed (NC). The potentiometer terminals are End 1, End 2, and Wiper. What a potentiometer does is create a variable voltage divider, where the wiper acts as the midpoint between two resistors to the ends. The series combination of the resistors always stays the same: so in a 10K pot, it is always 10 kohms; in a 100K pot, it is always 100 kohms, etc. The relative balance of the two resistors changes as you move the pot. In this way, if the two ends are connected to Vcc and ground, the voltage at the wiper will move between Vcc and ground as the balance of the resistors changes (voltage divider).An important idea here is that the potentiometer issymmetricwith respect to the two ends. When the wiper is closest to End 1, its voltage is equal to the voltage at End 1. When the wiper is closest to End 2, its voltage is equal to the voltage at End 2. So if your pedal outputs 0V when fully depressed, the wiper is closest to the End connected to ground at that position. To reverse the polarity of the wiper output, all you need to do is reverse the wires connected to End 1 and End 2. That's it.

author: inlanoche
author_rank: Newbie
timestamp: May 03, 2020, 03:45:36 pm
content: If I reverse the wires will this not effect the output?My brother has the wheel setup at his house now, so I will pass this on. I am assuming you are taking about placing new leads coming off the potentiometer?My thought was would be to (again, unskilled thoughts) would be to take the signal that goes from 3.2v (no press) to 0.1V (full press) and use it to control the resistance that could be tied to the power line coming out. The gauge only needs the signal and the ground . So if the device in question increases resistance when the signal to it goes up, this would reverse the range on the Vs to the gauge?Thanks.