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Was watching the CIA mini space shuttle do a perfect 10 auto landing on YouTube. Now my GRT HXr will fly me down to the runway, if there was some way I could use the arduino to flare........hmmm. |
Aviation-grade Arduino Controller
I've been heads down developing an aviation-hardened Arduino compatible controller.
This project started when I was discussing the procedure for a go-around in my Harmon Rocket with my wingman (Power up, stick forward, flaps up, trim down, call tower). He mentioned that I should just build a gizmo that would do the flaps and trim for me. Since I was already flying behind an auto-trim controller that I developed several years ago, I took this challenge on and reprogrammed the controller (in PIC assembly language) to implement this function. Everything worked out and now I have a single button push to dial in my flaps and trim. It even measures acceleration and runs the flaps all the way up if it predicts that I may exceed VFE in the go-around. I realized that many others may want a similar gizmo in their aircraft, but I wanted to move to the Arduino platform for ease of developement. The Arduino stuff is great, but it doesn't do a lot without adding on or designing custom shields, power supplies and packaging. The aircraft electrical and RF environment is pretty harsh. In fact, most of the avionics devices I have designed have most of the cost and circuit board area devoted to protecting the device from the environment (60 volt load dumps, reverse polarity, overvoltages on inputs, strong RF...). So I developed an aviation-hardened Arduino compatible board called the Falcon-AVR. The prototype has just finished Beta trials (one was replicating the auto-trim controller (1600 lines of C code), the other a marine instrument application). I have just implemented a board revision so that I can easily add-on WiFi or BLE or I2C modules, and support 28 Volt operation. My intention is to go 100% open source on this design. See this link for complete documentation. My intention is to provide blank circuit boards (plus a Digi-Key parts list) to interested folks. There are are assembly options, so some hardware smarts are required. Send me a p.m. if you are interested. Photo of initial proto below. Cheers, Vern |
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Vern, maybe you can help me. I need to protect the arduino H Bridge from back emf when I use the backup flap switch. Usually a diode is installed across the DC motor, however, our flap motors are bidirectional. Any thoughts ?
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On the Falcon-AVR, I chose to use relays to drive the flaps (or lamps or pumps) because they can be 'hostile' loads. Instead of catch diodes, I used a bidirectional Transzorbs, but the principal is similar. V ![]() |
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In my setup the arduino activates an Elecrow H bridge that then feeds through a relay to the motors. On the NO side of the relay is a manual flap/trim switch so I can still operate the flap/trim if the arduino fails. With the arduino off, when I operate the flaps with the backup switch, on release of the switch the LCD display attached to the arduino momentarily flashes. It seems the back emf is going through the relay NC side and through the bridge and into the Arduino. So I need to stop the back emf on both leads to cover up and down flap operation Could I connect a MOV across the flap motor ? |
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I don't write anything to the PMag other than the command to put it in serial streaming mode so it can be monitored. Here is the old thread that was created back when I was building it.... http://www.vansairforce.com/communit...ighlight=p-mag |
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To prevent this, you have to have isolated power, which is a challenge with semiconductor motor drivers. A MOV or a Transzorb won't prevent back feed because you can't fine tune the clamp voltage accurately. I would try the 4 diodes but to a completely separate 12V and ground. You may also try schottky diodes so that the catch diodes in the MOSFETs don't engage. This should do the trick. Edit: further reflection says that your Arduino must be powered at all times. The lack of circuit isolation is a challenge to overcome. It's what I meant by 'aviation hardened'. There are a lot of little gremlins when using the Arduino stuff in an aircraft environment. V |
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