A better failsafe: one fifth the size, one fifth the price

The more we get into the RC world, the more we're shocked by how overpriced and underpowered a lot of RC equipment is. Most of the specialty electronics, from ESCs to servo amplifiers, are just cheap PIC chips with a few support components. The parts cost a few dollars, but the completed boards often sell for as much as ten times that

A good example is the failsafe/multiplexer ("MUX"), which allows you to switch between two inputs for RC control (in our case, that would be RC or autopilot control). The main one on the market is the RxMUX, which costs $79 (shown below).


We thought we could do better. So Jordi created the DIY Drones Failsafe/MUX (shown at the top of the page), which uses the same Attiny45 and multiplexer as ArduPilot. Ours is $16.90, and is literally both one-fifth the size and one-fifth the price as the RxMUX. It also includes all sorts of other goodies, such as recognizing the middle position of a three-position switch and having a programmable signal-loss behavior. Plus it's open source, so you can do anything you want to the code.

Our failsafe/MUX is four channels, rather than eight (everyone preferred the smaller one and thought four channels was enough) but if you want an eight channnel one like RxMUX we can make it for you easily for about the same price.

Here are the two side-by-side, with a 9V battery for scale.


What else can we take 80% of the cost and size out of?

Views: 1468

Comment by NorthSweden on May 25, 2009 at 2:16am
So true about the prices, i can just say if you want to buy some esc, servo, battery and motor. just buy from china,

It is thieft.
Comment by jonny on May 25, 2009 at 2:36am
I think most people prefer to support a small enterprise that also supports YOU after you buy, rare comodity these days, after sales! Roll on the servo amplifiers and ESCs I say.

Moderator
Comment by Robert Krogh (hooks) on May 25, 2009 at 8:32am
In EU you will be charged a EU import tax 20 % + Customs tax 5% here in Denmark. Buying from USA or other contries outside EU :-( But if the package are send as a gift it we not be charged with taxes at all.. Hope DIYDrones will send me alot of "gifts" :-)
Comment by Noth666 on May 25, 2009 at 9:23am
I've also been thinking of making a *proper* programmable ESC for UAV use, the ones on the market are mostly over 100$/euro while they lack any advanced functionality.
I think an ESC which would report power consumption and other data to the uC without external gear and also be fully serial or usb programmable would be quite handy.
Comment by Joseph Glanville on May 25, 2009 at 12:21pm
In the RxMUX's defence it is an 8 channel multiplexer, double that of Jordi's DIY Drones Failsafe/MUX.
However I do agree that the DIY drones opensource alternative is the better option, most people don't need to multiplex more than 4 channels anyway.

Developer
Comment by Jordi Muñoz on May 25, 2009 at 1:15pm
The cost to add 4 channels would be 5 to 10 dlls more i guess. Still under that price ;-) But of course the board will be double sized just because the pin headers... I will develop in the next months the 6 channel version...
Comment by Curt Olson on May 25, 2009 at 1:27pm
There are many embedded computers that don't have good PWM output, but do have a serial out. One extension to this board that I think would be useful (or I would find useful) would to add a serial connection so the embedded computer could send servo positions as a serial stream.

In otherwords it would be like one of those serial servo controllers (pololu makes such a beast) but it would also mux between that and the receiver servo commands. I'm not sure if I'm explaning that very well, but hopefully it makes enough sense.

Extra credit would be to add funtionality to read the reciever servo commands and send them back to the flight computer so the flight computer knows the transmitter stick positions. This would be useful for logging manual flight data, or doing computer assisted flight like the Atto pilot does. (i.e. stick position would command a roll or pitch rate, and if you center the sticks, the flight computer would hold the current pitch and roll angles.)

Hide one of these systems in your airplane and you could really impress your buddies with your smooth flying skills ... even in really tricky winds.

Regards,

Curt.

Developer
Comment by Jordi Muñoz on May 25, 2009 at 1:40pm
Let me write it down.. Done. Thanks!! You are mainly talking about ArduPilot... You can program it to do that...
Comment by Jack Crossfire on May 25, 2009 at 2:47pm
It costs around $11/hour to live in Calif*, so it really depends on who's paying for the cost of sitting in Calif* running Eagle to design the product. $17 definitely is a charitable donation of $62.

Most day jobs in the private sector are starting to consider all time off as a company expense. In most jobs, if the boss found out you were selling something on weekends for $17 that cost $75 in your salary to produce, that would be bad 4 U.
Comment by Curt Olson on May 25, 2009 at 2:48pm
That might be an interesting idea. What's the size of the ardupilot compared to Jay's RxMux? Might have to take a closer look. Thanks,

Curt.

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