Yacht race timer

[KerryFenn]

Hi, don't know if anyone can help. I teach at the local sailing center and I am trying to come up with a race timer for dinghy sailing where we may be running 50 or more races in a day. The timer obviously has to be waterproof and will run off a 12v battery. The starting rules require a 3 minute countdown with a different coloured flashing light (similar to emergency services vehicles lights) activated at each minute as well as a horn sounding momentarily at the same time. The controls should be limited to a start button and a reset button with maybe a LED to show its ready.
I have no problem with the mechanicals but I am not sure what kind of chip would be best suited nor am I familiar with the code.
Any suggestions would be greatly appreciated.
Kerry

[Unsoundcode]

Hi Kerry, this would be a nice project to do with a BS2 and DS1302 timekeeping chip. Depending on how accurate your timing needs are you could probably time a 1 minute interval close enough without the use of the DS1302.
There would be plenty of room for your program and space left for a few additional features. I am sure you will get a lot of satisfaction if you build and code this yourself, but if you run into problems and have more questions post them here and you will get the answers.

regards
Jeff T.

[KerryFenn]

Thanks Jeff, It seems that the BS2 is the way to go. I will research lights and horn and see what we need for power requirements and take it from there.
Kerry

[KerryFenn]

Jeff, back on the project after a bit of a hiatus!!! Got some code written and it seems to work well enough with a buzzer and LED's to go a bit further. I may need some help with fine tuning later but am encouraged so far!
Questions:
What can you supply in the way of BS2 development boards and relays sufficient to drive a 12v airhorn and 12v emergency rotating lights.
I presume I can run the chip and everything else off a 12v battery?
Will the BS2 pin outputs drive the relays directly or do I have to use transistors?
Thanks,
Kerry

[John Twomey]

Kerry,
If you build your circuit and want to use 12v supply - use a 7805 voltage regulator (5v regulator)- so the BS2 is supplied with 5v - use a transistor to switch in a relay to switch in 12v to airhorns. Ensure you use a reverse biased diode accross the relay coil to protect the BS2 from damage due to back emf. Alternatively you could use a DC load type SSR - these can be switched directly from an output pin of the BS2 to switch 12v to your airhorns. Have you measured what current you will be drawing ?

Regards,
John