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Hartwig

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Posts posted by Hartwig

  1. Hi jbourdon, in this thread:

    http://www.rc-cam.com/forum/index.php?show...wtopic=1222&hl=

    you can find information about some easystar setup.

    Something about motor mount:

    http://www.rcgroups.com/forums/showthread.php?t=566537

    Another nice page is this one:

    http://www.mpx-easystar.de/

    It's a german page but it should be easy to understand the most important things.

    http://www.rc-cam.com/forum/index.php?act=...ID=in&MSID=4371

    ...and this one might answer some of your questions:

    http://www.rcgroups.com/forums/showthread....iloting+project

    Cheers,

    Hartwig

  2. Hi Doofer, the syncs need to be in "good shape" and the video levels must be correct, that means from 0V to 1V absolut range, not more, not less. (a little overhead of up to 0.2V might be tolerated by most devices, but that is not a "Must". However there must not be a DC offset, and the video level of black must not be lower than 0.3V! Otherwise it will screw up your syncs.)

    You might like to take a look at this page for a simple example of the video waveform (vid_wf.jpg) :

    http://www.rc-cam.com/lawmate.htm

    As a real life example, I attached a pic that shows the waveform of a black screen with a light grey vertical bar in the middle of the picture. (Timebase 10us/DIV).

    post-5-1185291378_thumb.jpg

  3. This is hard to judge without a look at the signal's waveform. You could try the following instead:

    1) Place the camera in a dark room or just put its lid over the lens to cover it and see if the the strobe effect still occurs.

    In comparison to that vary the amount of exposure up to bright day daylight and see if there are any changes in the amount of strobes.

    2) However you might like to try another camera with your TX/RX setup as well, for example the AV-out of a camcorder.

    3) Put the video amp/splitter in series between the camera and the transmitter and play around with the levels. If this helps a next step could be to adjust video level sensitivity on the lawmate.

    But again, I would definitely try to get access to an oscilloscope, maybe there is a friendly TV-service near your place where you could ask if you could bring your setup to have a look at the waveform. It takes about 10 minutes, so it should be not too much trouble.

    Cheers,

    Hartwig

  4. I got two brandnew identical Airwave TX612 modules which perfrom very well, but I got one problem:

    They have different sensitivity on their video input. While using the same receiver I get a little less than 1Vpp with the first module and about 1.1Vpp with the second.

    I heard rumors that the video level sensitivity of the modules can be adjusted using a little pot located inside the "sardine can".

    Does anybody know if this is correct, and if so, how to locate that pot? I don't want to screw up the precious thing by destroying a factory set parameter.

    On the picture, which I attached, you see the TX module with its upper lid taken away, so you can see the two pots that I discovered. The upper one, located at the upper left corner of the picture, is also accessable through a hole in the lid.

    Any help will be greatly appreciated!

    Thanks a lot in advance,

    Cheers,

    Hartwig

    post-6-1184512867_thumb.jpg

  5. Whenever you place complex loads like motors on a shared power buss, you should always be prepared for trouble. Not that it is absolutely necessary, but a no-brainer solution is to use separate supplies. A common ground can also be used if it is a star arrangement.

    If it was me, I would stick with a good hobby servo rather than a stepper motor. In this application it seems to me that it would be much simpler to deal with.

    Exactly. I would strongly recommend to apply the seperate vreg solution. This will definitely get you out of trouble, even when your power source gets weak or messed up with other stuff. You can also add another servo, if needed. Just power it from the servo supply. Doing this with only one vreg, would most likely show up with distortion again because the passive filtering might not keep up with the higher current.

  6. Just a little add-on: The switching regs of Dimension Engineering are great from my experience. However if you should have problems with interference, you can try adding a few low capacitance caps as well because the big cap might be too sluggish to compensate the high frequency components of the reg's switching.

    I tried the DE-SW-Regs as a BEC and my RC-receiver just refused to work. The "Filtering-method" with the linear reg, which I described before, solved the problem.

  7. Of course, if the signal is already terminated on this side, no second termination should be applied.

    You can daisy chain quite a couple of video devices, just make sure the first as well as the last device of the chain is terminated with 75ohms.

    For example, a camera has an output impedance of 75 ohms at its video output connector. So when you connect it (for example) to a Monitor, the Monitor needs to have an input impedance of 75ohms to perform proper termination of the transmission line. You can hook up another device between the camera and the monitor as long as this device has a high impedance input >> 75ohms.

  8. For what I suppose those receivers have comtech modules inside which need a certain voltage to operate properly.

    If the circuit which the manufacturer designed permits, it might be possible to go as low as ~8V. The standard circuit at the moment requires more than 9V since there is linear reg for 9V output which supplies the audio demodulator IC, as well as a couple of other components. So this might get difficult then.

    However, it seems that the comtech modules themselves seem to operate at voltages below 9V, as long as the voltage at the VCO power supply pin is high enough to ensure proper regulation.

    Further information can be found here:

    http://www.lechner-cctv.com/download.php?F...M2400RTIM8B.pdf

    On Page#5 you'll find the pinout of the module, look for Pin11.

    http://www.klein-electronic.de/download/DF...400RTIM8-00.pdf

    On Page#2 you'll find the default schematic.

    I hope this might help a little.

    A short word regarding switching reg versus linear regs:

    Switching regs have a slower responce to input voltage changes as well as load changes compared to linear regs, and, as VRflyer said, they might emit electrical noise due to their switching which might cause interference with sensitive components as receivers.

    However, in the schematic of the standard circuit for the Comtech receiver you can see that they use a switching reg, just give it a try.

    The best results I got was the combination of a switching reg in series with a linear reg. The sw-reg gives a suitable voltage to put into the linear reg, just high enough to ensure proper work of the lin-reg. This way the lin-reg doesn't get unnecessaryly hot. The lin-reg actually performs as a kind of "noise-filter" which reduces noise on the power wires.

    cheers,

    Hartwig

  9. Actually I didn't want to chime in, but now I must say that from my point of view there might be some misunderstanding regarding wallaguest's reply.

    I guess wallaguest posted this picture to show that it's possible to mount this type of lens to this specific camera, while from my experience, the lenses of this type differ in the position of their thread.

    The camera looks very similar to one that I have, and mine is a CMOS type. So that would explain the problems regarding exposure-changes. A CMOS camera will not perform as well as a CCD type when pointed into sunlight and then back to darker places. It needs about 4-5 seconds to accommodate. A CCD camera needs just about 1 second. So that's by design :rolleyes:

    Since doug2171's initial question was about the suitability of the lens (as far as I understood), wallaguest's reply was a picture that shows this camera with the different lens mounted for action.

    just my 2cents :)

  10. In case you like a shortcut solution, you might consider the MAXIM-ICs "MAX7461

    Loss-of-Sync Alarm" and "MAX4311" or "MAX4314" (High-Speed, Low-Power, Single-Supply Multichannel, Video Multiplexer-Amplifiers).

    There is a thread in this forum regarding a diversity receiver solution where a similar technique is required. You'll find the thread here:

    http://www.rc-cam.com/forum/index.php?show...topic=1324&st=0

    At the maxim-ic homepage you can easily order a couple of samples for free (limited quantity per person). If you need more samples of one special device, just ask your friends, relatives, neighbors,... if they might like to order samples for you as well ;-)

    Cheers,

    Hartwig

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