Smooth voltage rising - Page 1
Forum section: electronics / beginners

author: Milan78nis
author_rank: Newbie
timestamp: December 11, 2014, 11:40:21 pm
content: Hi.My name is Milan. My English is not too good but i hope that you will understand me and provide help.I want to correct accelerator pedal signal. signal voltage range is from 0.98V depressed to 4.5V fullpressed pedal.input voltage is 5v. when i hard step on the pedal, voltage jump is very instant and car hesitates.is it possible to make some simple electronics device to correct signal and slow down voltage jump orreduce rising to some point like 1.5V and than allow exponentially rising of voltage like without adevice. i was attached picture of what i want to accomplish.Any idea? Using transistor or FET in circuit or something else? Any example? Thanks in advance!

author: TKt48
author_rank: Newbie
timestamp: December 12, 2014, 12:44:02 am
content: Hi,You plotted voltage on vertical axis, but what is on horizontal one - time, pedal position?There is exponential amplifier based on opamp, diode and resistor. But you will need to adjust input and output voltage levels.

author: kxenos
author_rank: Frequent Contributor
timestamp: December 12, 2014, 01:26:29 am
content: You can test this circuit. Op-amps can be supplied from 5V but they need to be rail-to-rail. You have to select R1 and C1 according to your needs. For testing you can place a 1uF cap and a 100k pot and test it. The first part is just to simulate the pedal.Disclaimer: You should be very careful. Messing with your vehicle's pedals, brakes, steering etc. can get you killed. Be smart, be alive and leave your car alone!!

author: tggzzz
author_rank: Super Contributor
timestamp: December 12, 2014, 09:12:52 am
content: Quote from: kxenos on December 12, 2014, 01:26:29 amI wouldn't really be concerned if he kills himself, of course. But if he killed or injured an innocent passer-by, that would be a completely different matter.I hope this is only for a toy car, not a real car.

author: Milan78nis
author_rank: Newbie
timestamp: December 12, 2014, 11:58:01 am
content: I understand the risk but car isn't automatic. What is code for op-amps? i just want pedal to acting like it has very hard return spring and just for rpm from 800 to 1200 rpm because in that part car is jerking. that is signal voltage from 0.98V to 1.5V. is it possible to correct signal voltage depending of how fast is that signal changing? rc filter slows signal but in full range and causes override.

author: mikerj
author_rank: Super Contributor
timestamp: December 12, 2014, 12:44:52 pm
content: Why not fix the underlying fault rather than trying to mask the problem?

author: tggzzz
author_rank: Super Contributor
timestamp: December 12, 2014, 02:24:34 pm
content: Quote from: Milan78nis on December 12, 2014, 11:58:01 amYou don't understand what you are doing.You don't understand the subtle dangers.You will be a danger tootherpeople. (I don't care if you are a candidate for a Darwin Award, but I do care if you kill or injure someone walking past).Don't do itGet the car repaired properly by someone that has the relevant training and experience

author: rx8pilot
author_rank: Super Contributor
timestamp: December 12, 2014, 06:04:10 pm
content: Seeing threads like this makes me want to stay inside.

author: Seekonk
author_rank: Super Contributor
timestamp: December 12, 2014, 06:59:06 pm
content: Funny thing is there are people doing the opposite of this, making the voltage jump appear greater than it is in order to dump more gas in and making the mixture richer for better acceleration.

author: rx8pilot
author_rank: Super Contributor
timestamp: December 12, 2014, 07:23:02 pm
content: Any car modern enough to have pedal-by-wire will not let the mixture be influenced by the pedal signal. Making a richer mixture does not create more power, in fact it will create less power if it does not coincide with adding more air. So to solve that, the engine management will only add fuel if it is also opening the throttle body which will keep the mixture the same - just more of it. To ensure the mixture stays stable, there is a closed loop oxygen sensor that measures the actual mixture and the engine management has feedback from the real world. Making the pedal signal rise faster will only make the car hard to control smoothly. Maybe making the car "jump off the line" makes it feel faster.

author: electr_peter
author_rank: Unknown
timestamp: December 12, 2014, 07:42:48 pm
content: Quote from: tggzzz on December 12, 2014, 02:24:34 pmHave to fully agree with @tggzzz. Accelerator pedal control is crucial for safety and you could mess it up.Fix your car in professional shop or get a better one. And tell where you typically drive, so other people can avoid sharing the road with your dangerous vehicle.

author: Seekonk
author_rank: Super Contributor
timestamp: December 12, 2014, 08:53:23 pm
content: Quote from: rx8pilot on December 12, 2014, 07:23:02 pmThat's probably why you are not an any car forums. First, no one said anything about pedal by wire. Second, the TPS on the throttle body tells the computer the position of the throttle. Having it initially look more open than it is allows the injectors to stay on longer, dumping more gas. For a short period of time it ignores the O2 sensor and operates off a table.There are some that elongate the mounting holes of the TPS to make it look like the throttle is open more. Those that do that have the sensation of improved performance only works for a short period of time. The TPS is not a precision device. Software soon remaps the numbers after about 100 miles and things are back to normal.

author: rx8pilot
author_rank: Super Contributor
timestamp: December 12, 2014, 09:58:56 pm
content: TPS or wire does not matter - the bigger point is that making a mixture richer does not make more power.I am not in the car forums because I am in the airplane forums where we go fast for real.I designed and built race cars when I was young - mostly rotary Mazdas and Porsche 911's. Tons of fun, but it got boring once I learned how to fly upside down at 250mph and pull enough G's to pass out if I am not careful.

author: tggzzz
author_rank: Super Contributor
timestamp: December 12, 2014, 11:06:50 pm
content: Quote from: rx8pilot on December 12, 2014, 09:58:56 pmOh, that's not fun. You've got an engine to get you out of difficulties (until it fails, and dumps you in difficulties)How about 0-50kt in 4s, 0-2000ft in 45s.Normal trainers are aerobatic, with some aircraft certified to +9/-6G.All pilots have to demonstrate entering spins at 1000ft (and recovering) before they are allowed to go solo.Certainly fly much higher as well (10k-20k ft is standard, the records are double that).Vne is usually 150kt, with 192kt the highest available IIRC.Oh, you're taught to do loose informal formation flying before you go solo, tooNone of this rubbish about having to stay above 500ft, either - find a nice hill and follow it, eyeballing the sheep as they whizz past at 60kt.

author: suicidaleggroll
author_rank: Super Contributor
timestamp: December 12, 2014, 11:19:26 pm
content: Quote from: Seekonk on December 12, 2014, 08:53:23 pmActually yes, he did.Quote from: Seekonk on December 12, 2014, 08:53:23 pmWho said anything about modifying the output of the throttle position sensor? The OP said pretty clearly that he was talking about the accelerator pedal position, which means DBW:QuoteWhat cars are these that use the TPS to control fueling anyway? None of the ones I've ever worked on did that, it sounds horribly "guess and check", I can't imagine it's anywhere near accurate. The two systems I'm familiar with are MAF and speed density (PV=mRT, using the intel air temp, manifold pressure, and engine displacement*RPM to calculate the mass flow rate of air), neither of which would allow the TPS output to modify fueling, it would just piss off the closed loop control of throttle angle.

author: Andreas
author_rank: Super Contributor
timestamp: December 13, 2014, 06:22:42 am
content: Quote from: Milan78nis on December 11, 2014, 11:40:21 pmHello,its definitely not easy.Usually pedals with 2 independent and different scaling sensors are used.E.g. one sensor from 0.5 to 4.5V and the other from 0.5 to 2.5V or from 4.5 V to 0.5V.If you want really modify the signal you have to do the same pedal position for the two sensors.If the singnals are not plausible to each other the ECU will switch to limp home mode.It could also be that the pedal is defective if you have not a smooth behavior.So it would be better to check this and replace the pedal instead of using a not reliable cirquit.With best regardsAndreas