It hasn’t been that long since the last update, but so much has happened since then that I want to share it with you!
We are basically ready to order all the PCBs, go to tooling for the housing, and order all the other components including my favorite: one thousand pounds of special car horns!!!
This is going to be kind of long. Do you like the super-detailed updates? I hope so... but just in case I’ve put TLDR summaries at the top of each section.
We are making a sweet pushbutton to honk the horn with!
One of my goals in China was to find an existing waterproof pushbutton to use as a trigger for the horn. That didn’t go so well; we found one that was a proper switch instead of a momentary pushbutton (making a friendly honk really hard!), one button that wasn’t waterproof and one workable button for an cute bike siren but as pseudo-competitors the manufacturer didn’t want to sell any to us :(
But don’t despair, plan B is in motion and it is actually quite awesome. Chris (the industrial designer), the manufacturer, and I have designed an awesome button. The idea is that people will be able to clearly feel where they are meant to push by touch alone. This is really important, because as beta-tester Gregory put it “my finger hovers over the button instinctively when I see obstructions ahead.” Building the tool (production equipment) for the button, will go much faster than building the tool for the housing so it shouldn’t slow us down.
Also, a design change has been made to the connector. The place where the button used to attach to the housing did not have a robust enough connection. To solve the problem we moved the connection to outside the housing, and use a standard inline waterproof connector to make the button removable. Special thanks to the awesome guys at Revolights who hooked us up with a great supplier for this component. Their lights are the coolest by the way so check them out [http://revolights.com]
So soooooo close!!!
Details:Based on our experience assembling the CNC prototype we made some minor tweaks to make assembly work a lot better. There is just one more tweak to go-> adjusting the width of the location where the new button cable attaches.
Also the LED will now shine through two little circles of clear plastic. Our original plan of thinning the housing just didn’t work out any way we sliced it (too thick, LED’s are too dark; too thin and the wall is too weak). The new plan increases the cost, but we’ve got to know when the horn is charged...
There is a good possibility that more minor changes will need to be made by the tooling company, but the design is pretty much ready to be set in cold hardened steel!
There was a surprising problem; the manufacturer found the cause and fixed it!
There was a problem with the circuit board which caused our gating MOSFET (transistor) to overheat when honking for a very long time (upwards of ten seconds) or honking extremely frequently. The source of the problem starts with the battery. Our li-Ion batteries have a “protection circuit” which prevents them from discharging too quickly (which would damage them and potentially be dangerous). The protection circuit was set to allow up to 20amps to go through the horns which is higher than our MOSFET was rated to. The horn would fail when the MOSFET became so hot that it melted the solder off and lost the connection. The solution was straightforward, use a bigger MOSFET! A word to the wise though, it isn’t polite to honk for more than 10 seconds.
Not shipping in time for the the holidays
My heart sank when the manufacturer said it. Counting up the steps to shipping the horns, we just won’t be able to get them to you in time for the holidays. Best ship estimate now is early 2014. In Boston these are the days when it gets dark early and the roads can be slippery. Please hang in there and know you will be communicating with drivers with your very own car-sounding horn before you know it!