I provided Kids Ride On Push Car with some lights and sound indicator, to make my grandson happy. It was done some years ago, he was about three years. Nowadays he is still very interesting to use the car, as seven years old. The reasons are direction indicator lamps. Children like to play with switches and indicators.

Which indicators are mounted on car:

Direction Indicator lamps, blinking lights, switchable to left side or to right side. On each side there is front and back light. Frequency of flashing is about 0.5Hz.
Warning Lights, are all direction indicator lamps, blinking simultaneously and triangle shape light on dashboard with exclamation mark. All lights are activated by a switch on the dashboard, adjacent to a dashboard warning indicator light.
Sound of reverse backup sensor, this sound is known as beep signal during reverse driving. Normally there frequency change depending on distance, but in our case is frequency stable, about 0.5Hz.

Step 1: Parts

Used Parts are:

Main part is flashing LED, flashing twice per second, yellow colour, 5 mm diameter, 5pcs, flashing LED
Holder for 5 mm LED, 5 pcs, LED holder
Toggle switch, SPDT On-Off-On, 3 positions switch
Toggle switch, SPST, 2pcs, 2 positions switch
Universal diode, 2 pcs, 1N4148
Multivibrator, mini kit Flashing LED from Velleman, MK102
Resistor 82 ohm, 1/2 W
Resistor 47 ohm, 1/2 W
Active Buzzer, buzzer
Alkaline battery 4,5 V, type 3LR12, battery
tubing and cables

Flashing LEDs are type with clear lenses, but colour of light is yellow. Choose flashing one, not flickering. Toggle switch for direction indicator lamps must be single pole with three positions, middle position is OFF. Other switches could be any single pole switches. Maybe for Warning Light (Alarm) the best solution could be push button with indicator, type switch, with red triangle upper part, including holder place for LED inside. But I did not find such type of push button.

Universal diode is any type for forward voltage about 100 V and current 200 mA. Both resistors should be for power 0.5W. Active buzzer choose with higher sound output level and voltage for 5V. I have use 12 V, but sound level is acceptable.

For reverse driving sound, there is mini kit from Velleman. I prefer to use ready made kit, it is more simple. But you can make your own circuit - multivibrator according provided schematics. Or, there could be used any other kit with period time 0.5 s.

Required main tools:

Drill
Soldering iron

Step 2: Wiring Diagram

Electronic circuit is powered from 4.5 v classic battery type. This source is simple (does not require special care), small and powerful enough to last for a long time. In my case battery life was about 4 years, even with switches many times forgotten in ON position for a few days periods. I try to avoid charging battery, because it need maintenance and connection to charger (main power socket). During battery charging there could be safety risk for children. Anyway it is better solution, not to use charging battery.

Switch S1 is used for direction indicator lamps LEDs. LD1, LD2 for left side and LD3. LD4 for right side. Resistor R1 limit current for about 10 mA per each diode.. Nominal current for this LED type is 20 mA, but brightness for 10 mA is still acceptable. Lower current means longer battery life. Switch S2 switch warning lights or alarm. In this case all LED diodes are blinking, including LD5 in dash panel. Diodes D1, D2 separate this circuit from each side of direction LEDs. Resistor R2 limit current, both resistors should be 0.5 W. If you wish to slightly increase diode brightness, decrease value of resistors to 68 ohms (R1) and 33 ohms (R2).

The last switch S3 switch imitation sound of reverse backup sensor by connecting power to multivibrator module.

Step 3: Multivibrator

I tried to make project as simple as possible. By using flashing diodes I avoid using any interrupter. The first version of car was made with direction indicator lamps and alarm only, so electronic circuit was very simple. Later, I decided to add sound off backup sensor. For this reason there should be some type of interrupter and such requirement make circuit more complex.

I had idea to use flashing diode as component initiating interruption function, but it was not possible. Connecting buzzer with flashing diode in series does not bring desired effect (different current for each component). Even driving transistor by flashing diode was not successful. Finally I realized that, there is the only solution: an additional module - astable multivibrator. I simplified this task by using kit. Mentioned kit is small, adjustable for period and accept 4.5 V. Comparing to original kit, I omit LD2 and replaced it by buzzer, mounted outside of multivibrator PCB from acoustic reasons. Resistor R4 was changed to value 100 ohms. LED LD1 does not create any problem. Because of lower voltage is blinking with lower intensity and could blink invisible inside car or could be placed to dash board as indicator for reverse driving.

If you prefer to make this circuit by yourself, do it according attached scheme. Circuit is simple and could be done on universal printed circuit board.

Step 4: Mechanical Construction

For electrification is suitable any kids raid on push car made of plastic. There should be some access to inner part of car, as well as some small luggage space. In this space is located battery and multivibrator with buzzer. In my case it is space under seat, visible on photographies.

Start construction from mounting switches, find proper places and drill holes. I put switch S1 on steering wheel, in the middle part. In such way of direction switch mounting, steering wheel must have some mechanical limits for rotation as original design. It should be angle about +/- 60 degrees to each side. According my experiences I recommend to duplicate this limits by some wire plastic strips. Wires connected from switch, mounted on steering wheel should be free and able to adopt turning to each side. Put wires in tubing.

Other switches insert through holes, drilled on dash board near steering wheel. Put warning light indicator near switch S2 on dash board as well. Inner parts of switches are isolated inside tubing. In tubing with switches S1 and S2 are inserted resistor R1 and R2.

Next step is mounting direction LEDs. Locate places and drill holes. Remember to place these lights in such a way that during front and back collision would not be hit. Kid car is in very danger situation, it is in children's hands which are not very familiar to toys. For this reason, all parts and attachments should be strong enough. Therefore flashing LEDs need to be mounted in holders and fixed in position by clue, I used silicon.

If you have mounted switches and all LEDs, make wire connection. Solder wires on components directly. Using any connectors make construction more complex. Try to put wire in tubing and fix them as much as possible with wire strips. In places where components are mounting in difficult accessible place, solder wires on component first.

Finally introduce wires to luggage space and connect battery, multivibrator and buzzer. Power wires are soldered directly to battery poles. I recommend that you wrap isolating tape around multivibrator and attach it to battery with tape. Buzzer need to be mounted such a way that sound could be hear enough. Try find position and attachment.

I hope you and mainly your children enjoy this project.