Stop 12v remote ride on car jurking during start and stop. - Page 1
Forum section: electronics / beginners

author: diesel_508
author_rank: Contributor
timestamp: January 02, 2014, 03:22:45 pm
content: As above guys what would i need to add to the circuitry to make this happen so for instance it would take 1.5 seconds to get up to speed as not to give my little one whip lash as its quite brutal.I have googled for a couple of hours and not really got any where.Thanks for any help.

author: Rerouter
author_rank: Super Contributor
timestamp: January 02, 2014, 03:28:44 pm
content: ok, this took me a little bit to work out exactly what you want..to variably and with some level of ramping control the speed of your kids ride on buggy,if this is the case, have a look if the motor is a 3 phase one or just a big DC one (3 phase will have 3 or 4 same sized leads, DC will only have 2)in either case, you would either have to post some form of circuit design to modify the existing one, or look into a golfcart / e-bike controller with enough current to swap it out with.

author: AndyC_772
author_rank: Super Contributor
timestamp: January 02, 2014, 03:32:03 pm
content: Put a series MOSFET in between the battery and motor, and pulse width modulate the gate to control the motor current. Personally I'd do this with a PIC, but you could probably produce a suitable waveform with a 555 timer if you prefer. Use a low pass R-C filter connected to the on-off switch to control the duty cycle of the waveform.

author: Unknown
author_rank: Unknown
timestamp: January 02, 2014, 03:33:50 pm
content: It's more than likely a DC motor. Pretty sure I've done this, can't remember what I did though. If there's 2 motors you could have it run series/parallel for 2 speeds, and/or do the same with the battery packs to give more speeds. Probably find that you have 1 battery and 1 motor though.

author: Rerouter
author_rank: Super Contributor
timestamp: January 02, 2014, 03:37:42 pm
content: following andys post, i suppose you could build this circuit to take the throttle value in and vary accordingly,http://www.instructables.com/id/Yet-Another-Simple-Pot-controlled-555-PWM-generato/though that would not give you a gently ramp up, more direct throttle control.

author: fcb
author_rank: Super Contributor
timestamp: January 02, 2014, 03:53:40 pm
content: I'd second what AndyC_772 said. Use a BIG mosfet (with back-emf protection diode) and probably a small PIC - but this does depend on your skill level and time available.You could just use a big resistor (watts not ohms!) and a relay to short it out when the 1.5s is up.

author: TerminalJack505
author_rank: Super Contributor
timestamp: January 08, 2014, 07:56:55 am
content: Here's something I played around with in the simulator. It isn't a complete circuit since I don't know what exactly you are hacking it into but it is the non-trivial part of what you would need. It will produce the PWM signal that would drive the gate of an N-channel MOSFET.When activated (via Vin) the circuit will produce a 50% duty cycle signal and the duty cycle will increase to 100% over about 2 seconds. When deactivated it will go from a 100% duty cycle to a 50% duty cycle over about 1 second and then go to 0%. P1, P2 and P3 adjust the ramp-up time, ramp-down time and minimum duty cycle, respectively.The minimum duty cycle is meant to prevent a dead period since the motor likely will not start at lower duty cycles.You'd just have to interface the circuit to your particular input (gas pedal) and output (an N-channel MOSFET) and provide a regulated 9V power supply (an LM7809, LM317, etc.) Like others mentioned, don't forget a protection diode across the motor.All of the components are extremely common. So far as I know, Radio Shack in the US carries every single one of the components. It is composed of just one IC (LM324), two transistors, three pots and a handful of passives.Like I said, I have only played with the circuit in the simulator socaveat emptor.It may need some debugging.