Jugaad101 idea#2

Ever wondered how central locking of a car works? Do you know how speakers work? Heard of a solenoid valve?

Let’s look into how a simple and small device makes it all happen, before discussing how to procure this device quite easily, so that you could use it for your own projects.

Solenoid, a quick introduction

Click here if you want to skip the introduction.

A solenoid is a conductor coil wound into a tightly packed helix, which produces a uniform magnetic field in a volume of space when an electric current is passed through it.
In simple words, a solenoid is a type of electromagnet when the purpose is to generate a controlled magnetic field.

Solenoid coil
Image soure: Wikipedia

For people who are not familiar with the concept of solenoid, a simple solenoid could be visualized as a coil of wire wound around a hollow, non- magnetic cylindrical body. When a magnet (bar) is inserted inside this cylinder, and the terminals of coils connected to a battery (9V DC, for example) a magnetic field is set up passing through the cylinder making the magnet move in or out depending upon the polarity of the field generated. These motions are electronically synchronized and are used to produce sound by vibrating a thin film in speakers. Similarly, are the door locks opened in central locking systems.

WARNING: Do not, in any circumstances try the above experiment with ‘Mains’, the household power supply (220V or 110V). It might cause short circuit, and even fire! Also, the magnet may SHOOT OUT if the power supply is high, so face away from the solenoid and the magnet used in the experiment at all times.


During my undergraduate days, while working on manufacturing of a GoKart, my team was working on an innovation that required use of solenoids. But a big challenge was to find a suitable solenoid. Everyone did what you would probably do… Google search. And we found a huge number of small solenoids, mostly suitable for small robotics projects.

Buy Solenoid Google
Image: Google results

But the issue was: We were not building a toy or a mere working model. A person was to ride that car and we needed a robust mechanism with a powerful solenoid.

No issues, Google again… Look for powerful solenoids.

Next problem: We were undergraduate students with limited funds and had no intentions of making the holes in our pockets any bigger.

In the end we made a completely working system, found more powerful solenoids than we were initially looking for. Here’s how…

Digging up my past memories, I remember once when I, along with my father, had gone to get our car serviced reporting some issues with it’s starter motor (ignition, in other words) After examination the ‘starter motor coil’ was replaced and I grabbed the faulty component and again did the very obvious task with extreme curiosity: Googled…The coil was indeed a solenoid! I was excited to discover the solenoid is easily available, since every car has a self starting mechanism. You can now guess the number of these solenoids around you…

Car service

To know how an engine starter works, read this: (external link)

Let’s come back to the story where we were manufacturing a GoKart. It was then when we discussed this discovery and decided to give it a try. You wouldn’t believe we were able to get a ‘Maruti Suzuki 800’ starter solenoid for around INR 250. (Under INR 500, for sure)

The next challenge that you would face if you bought this solenoid, would be that you might not be able to figure out how to operate it! The issue is you will not get a manual to operate it. We ended up burning 2–3 wires daily before we figured out what was wrong, although the device is simple to use.

The engine starter solenoid User Manual

Buy Solenoid Google
Image: Solenoid Terminals

Simply put, connect the positive and the negative terminals as shown to a 12V battery (a higher current rating battery, or other DC source) with suitable wiring. Please note that thin cables will melt if used with the main terminals. You may use a thin cable with a switch for a signal from positive terminal of the battery to trigger the solenoid as per the need.

Adult supervision recommended. It is no game and lack of caution can result in serious injuries.


A starter solenoid is a cheap yet very powerful solenoid, which could be used by people from various streams and professions. Its availability is not limited to a single model. As you can expect, different types and models of vehicles require different sizes of solenoids, and hence the same are mass produced.
By now many ideas would have come to your mind regarding the application of the idea discussed here. If you have any queries or want to discuss something, leave your comments below.

Anirudh Sharma, QuarkMe Team