A couple of years ago I designed a pushbutton start for my Nissan 350Z. It consisted of a handful of automotive relays, some diodes, and the pushbutton from the Nissan Altima that features keyless starting. I really wanted to make it completely keyless, but there’s a chip inside the key that must be in close proximity to the steering column in order for the car to start. I didn’t want to disable any security features so this basically left me with a pushbutton start that still required a key. In other words, it’s just for fun and doesn’t add any convenience.
I designed the first version to allow the car to be started by the pushbutton with the key in any position, even in the ‘off’ position. This at least added a tiny bit of functionality. However, being an electrical engineer, I didn’t think about mechanical security devices. On my first test drive I left the key in the ‘off’ position, started the car with the pushbutton, and drove around my neighborhood. The steering wheel locked up about halfway through the first turn and I nearly took out a mailbox! I went ahead and left it installed with that functionality, but always turned the key to ‘on’ before using the pushbutton.
There is another downside to not needing to turn the key to the ‘on’ position. The button can be used as a virtual key and the car can be turned on (but not started) without a key at all. It would be easy to drain my battery by accidentally hitting it. Also, because of the location I chose in the center console, it’s also possible to bump it and turn the car off while driving (although you would need to hold it long enough for the engine to actually die).
I eventually got tired of these little nuances and decided to make a new version. I was also tired of mechanics messing with it and accidentally leaving the car on while it sat waiting for me to come pick it up after an oil change. I toyed with the idea of making a smarter button that can sense engine RPM, clutch position, and act more like an OEM pushbutton start. I would still have to insert the key, so this seemed like overkill for a mostly cosmetic mod. So I decided on an even dumber button than the first version, which goes against everything I stand for.
The new version I designed still consists of relays, diodes, and the Altima pushbutton. However, this version will only allow the car to start when the key is turned to the ‘on’ position. It also cannot turn the car off anymore. This is about as basic as it gets. The only reason for so many relays is to control the LEDs in the pushbutton and to prevent repeated starts. This comes in handy if I accidentally bump it while I’m driving. Here are some pictures of the installation and final product.
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