Velleman Parking Radar Kit
Avoid Fender Benders Using Ultrasonic Sound Waves
Description: Parking Radar Kit
Experience level: Intermediate
Time required: 2-3 hours (soldering required)
GoalTo build a simple radar kit capable of helping you in tight parking situations, or as the perfect set of eyes for your next robot.
IntroductionWhenever I start an electronics project, I like to look over the manual, and it is almost always possible to break the project into a series of steps. Below I have broken up the project into the steps outlined in the manual and described some of my electronics tips and tricks in building the Parking Radar Kit.
Base and Receiver Construction
JumpersMake sure you put the jumpers at the J locations on the PC board, not J1 and J2. I did not realize this and ended up having to unsolder the jumpers when I found the correct components for J1 and J2.
DiodesMatch the band on the diode to the band on the silkscreen. If you suspect a problem with one of the diodes, use a voltmeter to measure the forward voltage drop, which should be around 0.6 Volts.
CapacitorsOne of the capacitors on the base and two on the receiver are electrolytic - meaning, that they are polarized. The negative side (short lead) is marked on the capacitor, while the positive side (long lead) is marked on the silkscreen. If you put an electrolytic in the wrong way, it lets off some particularly acrid smoke, and it is a definite sign you have put one in the wrong way. It can be difficult to tell which capacitors are which. Make sure to double check the capacitor's number with the number in the instruction manual.
From the left to right the capacitor values are: 12pF, 22pF,
100nF, and 10nF labled 12, 223, 104 and 103 respectively
Showing how the screw
Screw ConnectorsThe screw connectors slide together nicely for a good fit on the PC board. Just be careful not to push them down onto your fingers.
Integrated Circuit (IC) SocketsEven if not provided, always use IC sockets if you have integrated circuits. It is terrible to have to remove a 16-pin IC from plated holes when it starts getting hot and smoking. On the PC board, it shows you where to position the notch of the socket. Always line up the notch on the socket with pin 1 of the IC to remove any confusion about which way the IC should go. In this case, right above the notch is the number of pins the socket has if you cannot tell which end is which.
Number above the notch and the notch (both at bottom)
Two plastic speedy boxes
Finding the center on a case
Case ConstructionIt is without a doubt these boards need enclosures. I chose two plastic Speedy Boxes. Below details my construction of the boxes using these enclosures.
Screwing in the PC BoardThe first thing that had to be done was to drill holes in the enclosures for the PC boards. Just to look nice, I centered the PC boards in the boxes, then laid the PC board down on the markings to find where the holes in the PC boards were. I used a 0.120 inch drill bit (size 31) with 1/8-20 (or so) machine screws, which took a little bit of elbow grease to get in. However, a 1/8-inch drill bit would have worked just as well and required less manual labor.
Screws and Nuts
Sensors Mounted in the Case
Sensor Holes and Filing Tool
Speaker InstallationThe receiver board has two sensors on it. To ensure they did not get blocked by the case, I decided to mount them outside the case and run wires from them to the PC board. The sensors are 0.7 inches in diameter, so I used a 5/8-inch drill bit and filed out the hole to make the sensors fit. If you do not have this size drill bit, a 1/2-inch bit works great, but requires more filing.
Final ConnectionsThe final step is connecting the base and the receiver together via the screw connectors. In total, there are six connections between the boards that have to be made. I used shielded five conductor cable. To make a sixth conductor, I cut back the shielding all the way to the insulation and soldered a piece of wire to the shielding. If you do not have multi-conductor cable, you can always string wires between the screw connectors too.
Modified 5 conductors cables
Putting the cables into the screw connectors
Final ThoughtsTo power the parking kit, I attached two wires to the final screw connectors and attached a 9 Volt battery to one. To complete the connection, I used a nickel from my wallet connected to the negative end and also used it as a "ground." It worked perfectly.
If you want to use this as a parking aid, connect the ‘+’ wire to the reverse light wire on your car and the other end somewhere on the car's chassis. The trunk should have no problem closing on the six conductor cable if you put the receiver outside the car and the base inside it. In order to keep the receiver attached to the bumper of your car, you can either drill holes in your back bumper, attach it with an industrial strength adhesive (like super glue), or use judicious amounts of duct tape.
Just as a final word of caution: Unlike conventional radar in which a Doppler shift in radio waves is measured, the Parking Radar uses sound waves. If an object is close, more sound waves return, and a greater voltage is induced in one of the sensors. If this voltage is large enough, a sensor sounds. However, some objects are better or worse reflectors of sound than others, so be careful not to rely only on the Parking Radar when backing up. And finally, have fun and park safely!
Ben Godfrey is an electrical engineering student at the University of California, Davis. Ben has written iPhone applications and is a Ham Radio operator.