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Post by michaelg on Feb 2, 2007 16:35:40 GMT 10
Hey guys, I've just ordered one of those el-cheepo rc planes off ebay for modding purposes. It only cost about 50 bucks, assuming it can fly I'll be fiddling with it and moding the crap out of it - hopefully it'll be powerful enough to carry a payload (and release on command) once i remove some 'non-essential' parts Has anyone played around with these things before? Looks like it could be alot of fun seeing what a pic can do on these babies
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Post by Dingo on Feb 2, 2007 17:53:29 GMT 10
I've not played with one but there are a few videos on the net of them, they seem fairly decent park flyers. One of these days I'd like to have the time to add microcontrollers to one of those el-cheapo helicopters Anyway, tell us how it goes and post lots of pics
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Post by michaelg on Feb 9, 2007 12:26:26 GMT 10
Hey guys, I finally received my first cheepo ebay plane. Its got 4 motors, and turns by shutting off 2 motors on either wing. This is my first rc plane - i was surprised at how much thrust it produced! I'm sure it'll be able to carry some stuff after some modifications - looking forward to seeing what i can do with this. Anyways, i took it to the park for its maiden flight. Threw her up into the air and she climbed very nicely! Made a right turn - mustve turned too hard because she went down broke into 3 pieces. Sticky-taped it back up, threw her into the air - same thing, except this time 2 motors on one side no longer work Should be easy enough to fix. I'll need to improve my flying skills before I start modding. If ur gonna play with these RC planes, i suggest u dont buy an expensive one to start with The first mod i think i'll do is change steering to use flaps, rather than shutting down 2 motors. Cheers, Michael
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Post by Dingo on Feb 10, 2007 12:20:43 GMT 10
Sounds like fun, got a link to the ebay retailer or a website showing the model?
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Post by michaelg on Feb 10, 2007 23:02:38 GMT 10
Hey Dingo, Here's the link from the one i bought ... cgi.ebay.com.au/New-RC-Remote-Plane-B52-Bomber-Aircraft-Aerial-Eagle_W0QQitemZ200077392756QQihZ010QQcategoryZ2563QQrdZ1QQcmdZViewItem... this guy is pretty good, i got it in less than a week. If ur patient u can get one cheeper than this though. I got the 2 motors working again, gonna replace the body with a balsa wood stick to lighten it, that'll give me some more weight to play with. Im planning on rigging up a fishing lure, and flying it out rather than casting it - should be able to get it out into the water alot further. Got one of those transmitters and receivers from Jaycar today - gonna use that for the release on the "bomb bay" Cheers, Michael
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Post by michaelg on Feb 14, 2007 10:10:14 GMT 10
hey there,
Well, ive replaced the body of the plane with a balsa wood stick. Got some good flights out of it, but now its been crashed beyond repair. Ive got another plane on order (different model this time), and one of those tiny IR helicopters on order.
Anyways, I pulled appart the transmitter and receiver from the plane. Turns out these things are very easy to hack into! Theres a chip on the receiver and transmitter with a pin each for up, down, left, right. I'm in the process of wiring up the receiver and transmitter to PIC microcontrollers, and will use the left/right signal to send binary data (1 and 0 respectively). That should give me unlimited "channels" to control all flaps, bomb bay, - full function on a 2ch remote control. Would be cool to use this on a robot with heaps of servo's etc. controlled by a PC (for house cleaning or whatever).
Cheers, Michael
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Post by michaelg on Feb 15, 2007 19:31:59 GMT 10
Hey there,
Just a quick update on the above, in case someone else stumbles across this thread and is contemplating doing the same.
It turns out that using this approach (using the existing pins on a TX/RX) is too slow for this. I can transfer 1 or 2 bytes per second reliably at most. If the pulse is any shorter it isnt registered.
Gonna start from scratch now with those Jaycar transmitter and receiver circuits instead.
Cheers, Michael
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Post by Dingo on Feb 15, 2007 21:19:34 GMT 10
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Post by michaelg on Feb 16, 2007 9:39:12 GMT 10
Thanks for the links Dingo. The ones I got from Jaycar look pretty much the same as those (and also 433mhz), they also cost around $10 each, so I'm guessing theyre pretty much the same. Has anyone by any chance used these in a project before? This is the first time ive played with RC, so I have no idea what i'm doing - if someone could give me a head start that'd be much appreciated. Been looking for tutorials on the net for RC NOOBS like me, doesnt seem to be much out there, but i guess the best way to learn it is by fiddling around with em Cheers, Michael
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Post by Robotman on Feb 16, 2007 9:54:17 GMT 10
There's some things about the Tx and Rx pairs that Silicon Chip made mention in their ? and ?+1 issues. I'll look up the dates when I get home and post them then. We're talking about the Jaycar modules here: 1) The Tx module (I think, but I'll check this) can run happily from as low as 3 volts, but will also run from 5V. The Tx module must also have a 10k pull-up to Vcc on its data line. This is because the transmitter only turns on with greater than 0V on its data pin. You can modulate in binary by pulling the data line down to 0V and back up again. You don't need a current limit resistor to 0V. (This is called On/Off Keying - OOK.) Or, you can modulate in audio by using a small amplifier with transistor output stage (taking the audio out from the collector). Maximum data rate is stated to be 2400 bits-per-second. You could more easily tie the Data and Vcc lines together with a 10k resistor, and supply Vcc from the Tx pin of your PIC. The current required is only around 10mA. Setup a 2400 baud data rate and do serial comms via radio instead of a 9-pin Sub-D serial cable! 2) The Rx module must run from at least 4.5 volts (preferably 5). It will not operate at less than this. The Jaycar data is wrong by stating 3V. Attach the Data pin (any one, they're all the same) directly to the Rx pin of your PIC. Use a 100k pull-down resistor if you're worried about noise. The Rx module will output LOW (0 volts) when not receiving anything - so I'm lead to believe. 3) The PDF data sheets require Asian Language (Chinese) character support to be printable, and even then it seemed liked a hit or miss affair. I was thinking of scanning these pages (that I eventually succeeded in printing) for the benefit of other DAAR members, but I don't know if that's legal. I'm not asking for money, and the manufacturer gets free advertising out of it - so who loses? What do you think Dingo? 4) I own both a Tx and an Rx module, but haven't used them yet. I think I will do some proof of concept testing on the weekend. Cheers P.S. Take a good read of this thread: www.picbasic.co.uk/forum/showthread.php?t=702especially the bit posted by NavMicroSystems on 1st September 2004, 17:37 (scroll down a bit to get there). Also follow the link to the Manchester Encoding. And the answer to $FFFF and $0000 is: you will get a DC level output.
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Post by michaelg on Feb 16, 2007 13:12:27 GMT 10
Thanks Botman, thats awesome your a lifesaver. I'll give it a whirl this weekend. btw do u know by any chance what range I can expect with these? I'm hoping to use it on my el-crappo plane - ive got some mini servo's on order, im planning on making the plane full function (attaching servo's to the flaps) rather than the differential thrust that it uses, and will connect a sidewinder 3d joystick to a PIC for the input controls (this joystick has throttle, and twist) Cheers, Michael
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Post by Robotman on Feb 16, 2007 19:33:39 GMT 10
Well, here I am at home at long last. I've looked up Silicon Chip magazine and Dec 2005 and Jan 2006 are the two issues that have the 433 MHz Tx/Rx info and projects. Remember, this info is about the Jaycar modules, which by all accounts, according to the article's author, are "most satisfactory." Apparently, the Tx module will operate from 2 thru 6V. The Rx module likes from 4.3 to 6V. Using a 170mm (17 cm, 1/4 wave) straight vertical piece of wire as an antenna will get you 300m line of sight signal range. The projects show a coiled antenna using insulated hookup (or maybe solid copper), wire just like a coiled telephone lead to save space. In some of the circuits, a 100nF capacitor is inserted between the PIC and DATA input of the Tx module, but in another there is just a direct wire connection. Try it with, and try it without. I think that it's probably there for "audio modulation" purposes. I guess that by supplying power via one PIC output, and the data signal via another PIC output, the Tx module can be powered up and its RF oscillator gets to stabilize before transmitting data. This might be a 1 millisecond delay - or maybe less, maybe more, I don't know because nobody really specifies it - although the link to the code below uses a "1 second warmup period": picaxe.orcon.net.nz/433txcw.basThis code also leaves the transmitter running for one second after finishing the output of data (the data should be at LOW) before turning the Tx module off. You could probably just leave the Data input at LOW and not worry about turning the Tx module on and off because the Tx only consumes power when its Data input is HIGH. Power for the Rx module (which uses even less milliamps than the Tx module) could also be supplied via an output pin on your PIC. This way you can turn off the Rx while doing a Tx, then switch on the Rx after turning off the Tx to get "full" half-duplex radio comms. (This is the same way that wireless PC networks work.) The antenna in this case can be shared through a CMOS switch (e.g. CD4066) which is gated using those same "power supply" output pins on your PIC going to the Tx and Rx modules. Or, you can simply have two antennas which is probably the cheapest and easiest option. Output a preamble of alternating bits at the start of any transmission. This lets the Rx module get a good lock on the signal. Using ASCII "U" is a good code because you get a start bit '1', then '01010101', then a stop bit '0', which is ten alternating bits. Repeat this a few (or four) times (a burst) at 2400 baud and then start Tx'ing your data (in Manchester format) - I'll leave the coding details of this as an exercise to the reader. Okay. I think I'm done. There's probably more questions to answers I haven't thought of yet, so cheerio for now!
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Post by michaelg on Feb 17, 2007 10:26:57 GMT 10
Botman, your a legend, thanks for that mate Much appreciated. Uve definetly saved me alot of time. 300m should be plenty for my RC plane. Just in case, ive also ordered a 315mhz transmitter from ebay that claims a 1000m range - although i doubt i'll be able to see an small plane 1 kilometer away Thanks again, Michael
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Post by Robotman on Feb 19, 2007 8:50:20 GMT 10
You're welcome, michaelg
I did do some testing of the [Jaycar] modules, as much for own benefit as anybody else's, and here's what I got:
1) Tx Module
a. Works fine at 3.3V (8.60mA) and 5V (14.20mA). b. The 100nF cap on the DATA input line isn't required. c. Adding a 100nF cap between the ANT output and GND works wonders to prevent the received OUTPUT signal (at the Rx module, and according to the trace on my CRO), from being seriously degraded when I held the Tx antenna with my bare hand.
2) Rx Module
a. Works fine at 3.3V (2.80mA) and 5V (4.30mA). b. Adding a 100nF cap in-line with the 170mm wire aerial and the ANT input also works a treat to prevent the received OUTPUT signal (at the Rx module, and according to the trace on my CRO), from being degraded when I held the Rx antenna with my bare hand. c. The DATA OUTPUT is inverted with respect to the DATA INPUT going into the Tx module!!! Yes, it's true - the CRO trace showed this plain as day. I could get a "positive" waveform by holding the Tx antenna in one hand and the Rx antenna in the other, but that's defeating the purpose of radio. I did use the same power supply rails to my breadboard holding both the Rx and Tx modules, so maybe that was the problem? But somehow I doubt it. This means that your data must either be inverted before transmission, or after reception. I think I should do some testing using a PIC on the transmitter end and a PC/Hyperterminal on the receiver side just to make sure. Maybe next weekend?
And now, here is some ASCII art circuit schematics. If this doesn't render as expected then simply copy and paste into your text editor of choice...
".\--+--/.............................................." "..\.|./..............................................." "...\|/..........................---.+5V..............." "....|............................|...................." "....|..........+----------+......|...................." "....|..........|..........|......|...................." "....|..........|..........|......|...................." "....+----------+ANT....Vcc+------+...................." "....|..........|..........|......|...................." "....|..........|..........|....../...................." "...---.........|....Tx....|......\...................." ".......100nF...|..Module..|....../.10k................" "...---.........|..........|......\...................." "....|..........|..........|....../...................." "....|..........|..........|......|...................." "....+----------+GND...DATA+------+--------<.Input....." "....|..........|..........|..........................." "....|..........|..........|..........................." "....|..........+----------+..........................." "....|................................................." "..-----..............................................." "...---................................................" "....-................................................." "......................................................" "......................................................" ".\--+--/.............................................." "..\.|./..............................................." "...\|/..........................---.+5V..............." "....|............................|...................." "....|..........+----------+......|...................." "....|..........|..........|......|...................." "....|..........|..........|......|...................." "....+---|.|----+ANT....Vcc+------+...................." "...............|..........|..........................." ".......100nF...|..........|..........................." "...............|....Rx....|..........................." "...............|..Module..|..........................." "...............|..........|..........................." "...............|..........|......10k.................." "...............|..........|..........................." "....+----------+GND...DATA+----\/\/\/----->.Output...." "....|..........|..........|..........................." "....|..........|..........|..........................." "....|..........+----------+..........................." "....|................................................." "..-----..............................................." "...---................................................" "....-................................................."
Cheers
P.S. As you've probably noticed, I've modifed this post trying to make the ASCII art retain the spaces I inserted, but this message board removes them. So, I've put in dots instead. Sorry.
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Post by Robotman on Feb 19, 2007 9:06:04 GMT 10
I've just had another thought about those 100nF capacitors...
Maybe they aren't such a good idea for long-range (> 20cm)!!! I don't know. How about somebody giving it a try? And what happens if the intent is to use these modules in toys that are always in close-contact groups rather than separated halfway across the backyard? Would the caps be a good idea then to swamp any coupled body capacitance (forcing the Rx module to lock onto a "constantly loaded signal"), as seems to be the case in my testing?
BTW, the Silicon Chip article also said that 20 ~ 50m is a good range for indoors.
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