Jump to content

robmitch

Trusted Member
  • Content Count

    26
  • Joined

  • Last visited

Community Reputation

0 Neutral

About robmitch

  • Rank
    RC-Cam'er

Contact Methods

  • Website URL
    http://
  • ICQ
    0

Profile Information

  • Location
    Tasmania, AUS
  1. robmitch

    RC Transmitter Tuning

    Well, I havent been able to get a 9C yet... In the meantime I had ordered a new antenna for my JR radio. Well, I would never have believed it, but I think it may have been the antenna !!! I have had no glitches since. Having said that, I havent had too many flights. There is also one other big factor: In the time it took for the new antenna to get here, I have changed to 2.4GHz Vtx. I will retry with my 900MHz Vtx (10mW and 500mW) soon and report back. Hopefully everything will be apples. As a matter of interest, I have great Video reception (2.4GHz) where I live (rural), but nearer to suburban areas, the reception is REALLY bad. I have only tried the one channel (Airwave 633module on ch4). Is changing channels likely to help much with that?
  2. robmitch

    DIY HT Noise/measurement issues

    Thanks, By the sounds of it, I am lucky anything is working at all. I will do some reading on mixed pcb layout etc. Thanks for the rough LC values. If that Futaba radio you have sitting around is a 9C and you want to sell it cheap - look no further
  3. robmitch

    DIY HT Noise/measurement issues

    OK, used HP filter reset at startup and it improved the transient from about 30s to 2s. However, this was using a third option for power supply - the regulated supply from the mcu development board... It has a larger 3.3V regulator and doesnt get very warm at all. The regulator on my custom pcb gets quite hot, supplying both the sensors and the development board (I measured 120mA, and my little regulator is rated for 800mA). The startup transient is still better using the HP reset (large zero rate values have gone) with my regulated supply, but the startup transient still takes some time to settle to a steady value (I am sure it is the reg output voltage is changing ever so slightly due to temperature changes on startup). The development board has a few peripherals that might be eating all that current, but maybe I am sinking (sourcing?) current from the sensor outputs into the adc of the mcu as well? Do I need current limiting resistors between the sensors and adc? Values? WRT LC's on lines, I dont have a Futaba radio What sort of LC values should I aim at?
  4. robmitch

    DIY HT Noise/measurement issues

    Thomas, 1) I thought simply grounding the 3 control pins of the gyro would save me time I will have to scrape some track off the HP line and try that. Good idea. 2) (Conducted noise) Toroid like the ones we use on servo cables? Should I also have any additional caps where power is supplied to the board (I already have the recommended caps on input and outputs to the regulators)? Cheers, Rob
  5. I have been working on my own gyro/acc/compass hybrid HT. I am using a 2-Axis accelerometer and single axis gyro, and a 2-axis compass sensor. These are all loaded on my custom pcb. I am supplying 12v power, gnd, PPM in and PPM out to the board via a 4' multicore shielded cable from my JR transmitter module. At the moment, however, I am using a Zilog mcu on a Zilog development board for processing, and it is connected to my custom pcb using a 8" ribbon cable (12 wires to the jumpers on the development board). I have been able to monitor the incoming PPM signal, modify the last two channels with either tilt or roll from the accelerometer output, and either pan using integrated yaw rate or compass heading. The aim at the end of the day is to use a kalman filter to combine yaw rate and compass heading to a pan angle. However, there are two issues with the yaw rate output that I need to resolve: 1) At startup, the zero rate reading starts at a high value and over a period of about a minute, it asymptotically settles to its zero rate value, which remains relatively stable from then on (If I supply power to the board via 12v wall-wort). Could this be due to a temperature transient at startup (the gyro should be fairly independent of temperature - in datasheet), or perhaps the voltage regulator 3.3v LDO linear on startup (the gyro output is ratiometric with input voltage)??? 2) If I supply the power to the setup from my tx (36MHz), I get the additional problem of small random variation in gyro output with tx proximity (even my hand coming within a couple of inches of the sensor pcb changes the output). The tx will be within a couple of feet of the unit at the end of the day, so I need to sort that out. What sort of power filtering should I have to the circuit - LC filter? Do I shield the circuit with a metal housing? Do any of the commercial HT's have any of that... I saw Melih's circuit board for his - it doesnt seem to have any filtering components at all?!? I have attached the STMicro gyro datasheet. I am using the suggested circuit on page 8 (4x rate output pin goes straight to ADC of mcu. From the gyro datasheet, this output is a high impendence buffered output). There is a filter cap on the input pin of the mcu development board too. Any issues to be seen so far? Cheers, Rob ly530alh small.pdf
  6. robmitch

    3.3 voltage reg for Aw633

    Right, now with a PCB, I wasnt confident getting thermal contact btw the module pcb and one of my own. I would have used the electric frypan method with solder paste on the main square pins on the module. But what do you use to get thermal contact btw the remainder of the two pcb's and not get any accidental shorts (my pcb would be mainly ground plane) - Oh, and you would want a 2-sided pcb with lots of via's for heat transfer to the outside face, correct?
  7. robmitch

    3.3 voltage reg for Aw633

    Kilrah, with work like this, I will probably never be let into Switzerland again Points taken - I will definitely do things differently next time. However, wrt the antenna, how would you get around having to have an sma connector etc (add lots of weight by the time youve put the mating connector and antenna on)? Cheers, Rob
  8. robmitch

    3.3 voltage reg for Aw633

    Sorry, no macro function on camera. Module is mounted on my crash-test plane . The piece of tin is soldered between the regulator output pin (large one) and the cap. This gives enough thermal mass for initial temperature transient (a minute or so before you need to have a slight movement of air). Small pin of reg soldered directly to the module supply pin, ground pin to module ground and input pin directly to 5V supply wire from BEC (separate BEC for camera and vtx). Oh, module is mounted with a gap btw module pcb and wing for airflow
  9. robmitch

    3.3 voltage reg for Aw633

    Mr RC-Cam, Good idea... as long as no-one laughs at soldering etc. Photos to follow Rob
  10. robmitch

    3.3 voltage reg for Aw633

    Cooool, Got the module working and had a flight today - works great. As mentioned, I used a 5V switching bec powered by the main flight battery, vsn505 5V camera from that, and then a LDO linear 3.3V reg on the module. I put a small piece of tin on the reg as a heatsink (basically a one-fin heatsink). I wouldnt leave it on without any airflow for more than a minute or two, although with the slightest airflow (say 0.5knot), I would say nothing gets over 50degC. I put a switch btw the battery and bec, so I power up plane/check controls etc, then power up vrx, goggles etc, then vtx. I was aiming at a very small/light vtx to put on the wingtip of a 300/400g plane. Weight ended up at 8g including custom dipole coax antenna (thanks mr rccam) I get a little noise in the video with increasing throttle, but not too much. I will prob use a separate battery for larger models, and maybe LC filter for smaller models (if I can make one light enough <_< ) Thanks for all the info guys, Rob
  11. robmitch

    RC Transmitter Tuning

    Thanks guys. I am thinking about getting a Futaba 9C instead, although, a second hand one. We use 36MHz in Aus. Does anyone know if the 72MHz US radio's antenna is that same as the 36MHz version used in AUS. That is, if I buy a radio from the US and buy a 36MHz module, will the antenna be as well tuned as if I bought a set locally? Also, what is the difference between a 9C and a 9Z? I take it these radios are able to easily physically change btw mode1/2 Cheers, Rob
  12. robmitch

    RC Transmitter Tuning

    Thanks Terry, Ron, I thought as much, but asked on the off chance... I suppose I can go and get a 2.4module, but then I need to change all my receivers and video freq... Ron, What is an X8 module? Terry, new aerial... What could go wrong with an aerial? Appreciate the replies. Cheers, Rob.
  13. robmitch

    RC Transmitter Tuning

    I have been having issues with bad glitches with my old JR X-347 radio. I have used it to tune servo movements and other PPM projects, while it has been turned on with antenna collapsed, which I now believe is bad for the RF circuitry. I am sure the radio is outputting a solid PPM stream, but the RF module is probably out-of-whack. What needs to be done to tune the circuit in the module? Cheers, Rob
  14. robmitch

    3.3 voltage reg for Aw633

    Having done a bit more reading, it looks like i will be asking for trouble if I have V/Vmax > 50%. I will stick to the 10V caps - that way I will have just over 30%, and reliability.
  15. robmitch

    3.3 voltage reg for Aw633

    Right, slight change of plan. I will now use 3s main flight battery... Use separate switching bec at 5v - 5A for receiver and 5v camera, and then drop that 5v down to 3.3v with the LDO reg on the tx module (with lots of filter caps). Can I get away with 6.3v 470uF tantalum caps for the tx module, or even 4V (these are on the output side of the 3.3v reg). I can get 10v ones, but much more expensive...
×