Q: GL writes: You talk a lot about big kid toys, but what about for actual kid cars? What is a cheap way to make a kid car speed control?
A: I find this to be an entertaining question and one I get quite often. So below is about as simplistic as it gets! There can be a lot of variations to this dependent on size of car and weight. Relays can be used for light duty instead of solenoids as an example. You just need to calculate the load and go from there. It has quite often been mentioned to me the kids see Dad/Mom driving around and they want one like Dad/Mom. So I hope this helps.
Battery positive is applied to all four solenoids. At the same time battery positive is applied to the foot pedal switch. When the foot pedal switch is closed battery positive is applied to all four speed switches.
Let’s say 1ST speed is selected. When the foot pedal is pressed battery positive is applied to the 1ST speed solenoid. The contacts inside the solenoid closes and diverts that positive voltage to R4 resistor. Because the other solenoid contacts are still open positive voltage flows through all the resistors. From R1 connection positive voltage flows through A1, A2, S2 and out S1 to battery negative. As each solenoid speed is selected the path of resistance through the resistors decreases and speed increases. Very simple and easy to do. If you want to spend a little extra you can do the same thing with a Solid State System. You can make a small car out of GO-Cart frames. Welded tubing and pre-existing kits cars you can find on-line. Should be a fun little project for a weekend or two. Enjoy!
Tech Tip: it is strongly advised to add a fuse on either the positive or negative main connection on the power side. The resistors allows you to have control of the car’s speed!
A good resistor to start with is part number 2699, motor 7954, solenoid 1128 and 9074 switches, or 2454 switches. Look for old junked golf cars and take parts off it. In other words look around there are used parts available. Use a belt driven drive unit off a lawn mower or industrial car. Be creative on that part.