Fangrui Product Details 7-70v 30a Pwm Dc Motor Speed Controller, Can Be Directly Connected To The Motor And Adjust The Potentiometer To Adjust The Motors Speed. Instructions For Use And Precautions:make Sure That The Positive And Negative Connections Between The Power Supply And The Governor Are Correct Before Turning On The Power. Reverse Connection May Burn The Circuit Board. Do Not Touch The Heat Sink With The Wiring, Or It May Burn The Circuit Board.(motor) There Is No Need To Distinguish Between Positive And Negative. If The Direction Of Rotation Is Wrong, Please Change The Two Wires Of The Motor. Note That This Is Not A Power Supply Module, It Must Be Connected To The Motor To Adjust The Speed. Without The Motor, The Output Of The Multimeter Not Change. It Is Suitable For Dc Brushed Motors And Cannot Be Connected To 220v Household Electricity. Used For Childrens Toy Carif The Product Is Used In The Modification Of Childrens Car, The Output End Of The Speed Controller Can Be Connected With A Forward And Reverse Switch To R