Hi. I'd just bought a go kart, and find the price of a decent lap timer very high, so I'd like to try making one myself. I've had electronics in (high) school (10 years ago), so my education in the field is not great, and I'm rusty of what I once knew. I do know though, how to program MCU's (ATMEL AVR's).
Go kart tracks - Lap timing system
AFAIK the system that makes commercial lap timers work, is that the tracks have a magnetic bar installed under the tarmac at (the bare minimum) the start/finish line. They also usually have some other bars installed to divide the track into sectors, making it possible to analyze lap times in 2-3 sectors around the track.
My idea
Put a hall effect sensor on my cart. Connect it to an AVR MCU, along with an LCD panel, and some sort of buttons to select the amount of magnetic bars for the track. Use the Hall effect to detect start/finish line and other sector-bars, and display the time of last lap on the LCD.
Problem
I ordered a basic Hall effect sensor to start with. I connected it to the ADC of an ATMEGA device. Without influence of any direct magnets, the ADC gave an input of ~ "140". With a (quite strong household magnet) at 3mm distance, it changed to "139", and then the value dropped almost to zero as the magnet traveled the last 3mm towards the sensor. The problem is the sensor doesn't register a thing until the magnet is 3mm away.
I need to detect a magnetic field that is probably 1" beyond the tarmac. Add to that, 1-2" of kart ride height. How can I accomplish this? I've not been to the track to measure the field of these bars. For all I know they might be "enormous" but I somehow doubt it (the distance is quite far).
So I was wondering if there is better sensors than the hall-effect sensor, or maybe other kind of it you would recommend me to use? The one I have now is a quite small sensor made for small PCB's. I reckon there exists something "industrial" that might be bigger, and able to sense at further distances.
Any other ideas (amplification etc) is also very welcome.
AFAIK, the commercial lap timers also use Hall effect sensors. That's why I pursued one in the first place.
Any help highly appreciated, to start brushing off some old electronic skills
Go kart tracks - Lap timing system
AFAIK the system that makes commercial lap timers work, is that the tracks have a magnetic bar installed under the tarmac at (the bare minimum) the start/finish line. They also usually have some other bars installed to divide the track into sectors, making it possible to analyze lap times in 2-3 sectors around the track.
My idea
Put a hall effect sensor on my cart. Connect it to an AVR MCU, along with an LCD panel, and some sort of buttons to select the amount of magnetic bars for the track. Use the Hall effect to detect start/finish line and other sector-bars, and display the time of last lap on the LCD.
Problem
I ordered a basic Hall effect sensor to start with. I connected it to the ADC of an ATMEGA device. Without influence of any direct magnets, the ADC gave an input of ~ "140". With a (quite strong household magnet) at 3mm distance, it changed to "139", and then the value dropped almost to zero as the magnet traveled the last 3mm towards the sensor. The problem is the sensor doesn't register a thing until the magnet is 3mm away.
I need to detect a magnetic field that is probably 1" beyond the tarmac. Add to that, 1-2" of kart ride height. How can I accomplish this? I've not been to the track to measure the field of these bars. For all I know they might be "enormous" but I somehow doubt it (the distance is quite far).
So I was wondering if there is better sensors than the hall-effect sensor, or maybe other kind of it you would recommend me to use? The one I have now is a quite small sensor made for small PCB's. I reckon there exists something "industrial" that might be bigger, and able to sense at further distances.
Any other ideas (amplification etc) is also very welcome.
AFAIK, the commercial lap timers also use Hall effect sensors. That's why I pursued one in the first place.
Any help highly appreciated, to start brushing off some old electronic skills