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About laserbounce

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    RC-Cam Visitor
  • Birthday 07/22/1984

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    Gainesville, Florida
  1. Giorgio, The length of the cables probably does not make much difference in that regard. The reason the image is dark is because both the glasstron and camcorder place a 75 ohm load on the video signal, but the standard impedance is a single 75 ohm termination to 1 volt peak-to-peak signal. If you open up the glasstron and camcorder and find a 75 ohm resistor near the input jack and replace it with 150 ohms and use a short cable, it would probably work fine. Regards, John
  2. Giorgio, Your gps is probably not transmitting as strong an RS232 signal as many typical RS232 devices do. The RS232 transmission voltages are probably in the -5 to 5 volt range (I forget, but it is much lower than normal RS232) instead of -10 to +10 volts as a computer or MAX232 will transmit. If you have another gps try it, or if you are good at building you may be able to find a chip similar to the MAX232 that will relay the signals to the higher standard levels. The PDC10 uses a receiver that is comparable to a MAX232, which should work in parallel circuits, assuming that you have a typical transmitter. Do you know what the receiver circuit in the overlay device is? Best Regards, John
  3. Bernard, You can get the dc-dc converters from digi-key.com As for the gps, I remember that I'm using a 150ma 3.0v regulator on my Etrex, but the thermal dissipation of the TO-92 case regulators may be insufficient for battery voltages over 7 volts, so you might consider a bigger TO-220. It works fine even with the backlight on. John
  4. It is difficult to determine without knowing the specifications of each device, as the current consumption for all those devices together could range from 200ma-500ma @ 12v. Also note the garmin etrex is not a 6 volt device, I believe the specified voltage is 3.15 +/- 0.15 and you can use a 3.0v 100ma regulator for this. For a battery you could use 10-12 AAA nimh cells or 4 lithium cells (with a regulator), but if your plane already uses a lower voltage pack, then you may want go with the low voltage pack and step-up the voltage with a DC-DC converter like the power trends pt5041. Regards, John
  5. Yes, I do agree the FMA co-pilot would probably be necessary to stabilize the craft. KE4UVQ, how accurate is your WAAS? And how wide a runway could you land on? My gps receivers seem to drift quite a few meters. I am considering ordering some high quality gps receiver boards like the Motorola OnCore that produces pseudo range output data streams, as the professional surveying systems have the accuracy, but are way to expensive. When using two receivers you may get data from different satellites and ionosphere propogation can result in several meters of measurement error in the calculations. I read an interesting website today of a university project where they tried to build a robot to automatically walk on sidewalks using a magellan dgps beacon receiver, and sure enough it wasn't accurate enough to drive down anything short of a double lane road. It appears we need to be able to compare the same satellite signals against each other over a small geographic area to get consistent runway accuracy in the one meter range. John
  6. Okay, I've been reading up on gps technology and am wondering if anyone has used DGPS (differental global positioning satellite system) in a model aircraft or even a land craft! DGPS is supposed to be accurate to a few centimeters by subtracting the coordinates of a gps unit at a known location to an gps unit at an unknown location nearby. The commercial jets have an automatic landing system that uses some kind of DGPS. If I put one gps in my plane with a Tiny-Trak like device and one gps plugged to my laptop at the edge of the runway and write software to control my radio transmitter through a trainer cord and the laptop is programmed to know where the plane should be at each point during final approach, do you think it would be accurate enough to safely land the plane? Any thoughts welcome. John
  7. Are you using the Epicwin loader software? If so, the configuration fuse options should be shown and selectable in the configuration menu at the top of the screen. Regards, John
  8. Hi Kin, The PIC navigates using the heading and bearing calculations that the gps has already measured, so it is just reading the NMEA sentences coming through the cable from the gps (bearing - heading = turn angle). We have had several discussions about gps altitude vs. barometric altitude and the gps altitude will not be as reliable as a barometric altimeter, but gps altitude can fly I just don't know how well. That would be great if you wish to rewrite the code in C, that way the code could be modified without buying a picbasic compiler. I have been working on the code for the autopilot w/gps altitude and it seems to be going well. It only requires two more pots, and two more servo connectors. though it isn't finished yet, as I'm waiting on parts to put together the prototype. Your project is really cool. Keep us posted on it as you develop it. Best Regards, John
  9. nice pics, mike. The translucent blue case is really neat! I just finished the code for the satellite altitude hold and elevator servo routines. It doesn't have pots for adjusting the gain, travel and direction of the elevator servo yet, and the cruise altitude is set in software for now (I live in florida, no worries). I am also considering adding a satellite signal failsafe that reads the number of satellites and/or HDOP precision (in meters) to provide for a safe altitude gain in case of poor signal reception conditions. Also replaced the Max232 IC with a transistor that inverts the voltage of the data line from the gps. If anyone want the source code, just email me. Mike, I enjoyed reading your webpage on the autopilot. Do you have any test results on it yet? Thanks, John
  10. Bruce, It looks like the poptronics multi-chip programmer only has a socket to fit the 16f84. The only hardware difference for a 16F87x programmer is a few pin connections moved around, and the IC-Prog software is likely compatible with the 16f87x series. If you can get ahold of a big 28-pin socket (or stick smaller ones end-to end) and then solder 5 wires (MCLR, Data, Clock, Vdd, Vss) to the new socket according to the 16f87x pinouts it should work. Best Regards, John
  11. Mike, Have you considered using the $GPGGA sentence to get the altitude position from the GPS, or is this less dependable than the barometric altimeter? It looks like many of the Garmins such as etrex do support altitude output. Yesterday I built a PC board and got the PicBasic Pro compiler, but I will probably wait until next week to give it a good test. Hey Bruce, we can send you the code in assembly if you don't have a Basic compiler. John
  12. Okay, I checked out the Yahoo rcpilot group and it seems like a great design. I'm looking at gps' that are lighter weight, but I have heard that the communication protocol of the Geko's are slightly different than other Garmin units, do you know what compatibility issues different models might have and if they are best suited to UAV usage? Mike, do you have a website where I could view some source code? I I would like to contribute to the project if I may. Thanks, John
  13. Mike, I have experience writing custom programs for PIC microcontrollers in C and assembly and etched a few custom PCB's. I tried searching the net for info about gps interface communication protocols and found a few sites, but I have not yet figured out how to implement it for plane navigation. John
  14. I am new to the UAV/RPV world, but am interested in building a small plane with an onboard digital camera and a gps for navigating the plane to a programmed coordinate location to take a picture. I imagine its been done before, but I would like to build the smallest and simplest design for it. I want to use an inexpensive gps unit like a Garmin Geko and interface to a microcontroller (like a PIC) that drives the servos. Do you guys have any advice or know any good websites that could assist me in developing it? Thanks, John
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