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  • Users: walker1
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  1. walker1

    7805 / 7905 Power supply problem

    We have eight IF boards in our equipment. Most of the IF part run on +15V. The last demodulator (controlled by a shift register running at 40 MHz) runs on +5V, and the ADCs run on +/- 5V. The analog filter on the ADC inputs runs on +/- 15V. The principle in the power supply is shown in the...
  2. walker1

    Implementing measured position AND speed in a Kalman?

    We need to slave our turntable to an external radar. We will also have to predict a little time forward in order to compensate for various delays. A Kalman-like approach seems a good solution. The radar delivers various data, including X, Y and Z position on the target, so standard Kalman can...
  3. walker1

    Slave to radar?

    Well, yes. This is mainly into algorithms, but I have not found a specific forum for that. We have a scientific radar we want to slave to tracking radars during aircraft trials etc. These radars usually deliver range, bearing, elevation, track and ground speed referenced to some point, if not...
  4. walker1

    Protecting flash drive in US-Mail?

    Not sure, if this is the correct forum, but here goes... I have received a SD card from my brother i Arizona. The drive appears to be completely defective upon arrival (does not show up at all), but working before it was mailed. According to this...
  5. walker1

    Can a smaller capacitor do it?

    Due to some error, we have been shipped a 3-phase 380V, 350W fan. We, hopfully, ordered a 230V single phase version, but do not have time for a replacement. I know we can create a semi-phase by using a capacitor. The datasheet covering all the "250" different versions (incl. 48V DC) mentiones...
  6. walker1

    Removing N-current at HV?

    My brother has asked me a strange question. Apparently the distribution lines (100 kV or more) are Y-coupled. But the neutral current is said to be nearly zero (1-2A), virtually no matter how unballanced the load on the 3-phase consumer net is. (400V European Y with high N-current) Can anybody...
  7. walker1

    Spicing Colpitt osc?

    I am trying to simulate a crystal Colpit oscillator in the free B2-Spice edition. (release 4.2.1) I do have oscillation, but only a few mVpp, and only very near a perfect sine. (No harmonics it seems :-( The crystal is composed of 20fF, 1.25mH and 30 Ohm resistor in series. All shunted by...
  8. walker1

    Overtone crystals?

    I will be needing a 1st LO at around 48 MHz. That seems to be in the 3rd overtone area. But a strange question just popped up. Does every crystal have useful overtones or do they have to be specifically cut to have that? I mean, could I take any, say, 16 MHz crystal, use in a 3rd overtone...
  9. walker1

    Kalman filter

    I am not quite sure where to place this, but here goes. I have implemented a 'simple' Kalman filter for 1 dimentional (range) tracking. It works for slow targets, but I kind of wonder, if it is correct, that the range gain always end up at exactly the same value no matter what I set the two...
  10. walker1

    DOS printing in Win XP ?

    My dad is using an older DOS program for acounting. Until recently it worked fine under Win ME. On his new PC he is running XP prof. and the software as such works fine. The problem comes, when he wants to print something. At times it works fine and at other times the Windows spooler crashes...
  11. walker1

    Solid-State relay for DC

    Someone just asked me, if it would be possible to use a solid-state relay to disconnect a 115-130 VDC line with an electrical motor as load ? As the motor will be inductive, I may have to add a fly-back diode with or without an additional resistor in series. But what else should I look out for...
  12. walker1

    Reach of a wireles network

    My parents want to connect my mum's PC on the 2nd floor to the internet, which my dad uses in his office in the basement. (only socket is located there!) They live in a standard Danish brick house from 1932 with, to my knowledge, no concrete or metal grids between the floors. The cheapest...
  13. walker1

    Turning model ?

    Not quite sure where to post this. If one has a scooter (two wheels) with a known overall length, wheel base and width, how do one calculate / plot the path it takes during a sharp 90 degree turn? Or in other words: Can I roll it into this holding area without having to lift it to get around...
  14. walker1

    FFT in FPGA?

    This was 1st posted under the PLC forum. I just had a request yesterday. If I would be able to create a small, say 4, 12 bit inputs, FFT in a FPGA ? We use the Altera Cyclone series, and Altera does have a MegaCore FFT, which, however, starts at 64 inputs and uses way too many resources in...
  15. walker1

    FFT in FPGA?

    Not quite sure where to put this. I just had a request yesterday, if I would be able to create a small, say 4, 12 bit inputs, FFT in a FPGA. We use the Altera Cyclone series, and Altera does have a MegaCore FFT, which, however, starts at 64 inputs and uses way too many resources in the...
  16. walker1

    10 MHz linear amplifier using HCMOS ?

    Way back, when I designed this input, I put in a standard transistor stage in order to boost the input 10MHz sine wave to something a 74HC14 could handle. As it much later turned out, the input level was about 1.5Vpp, so I have had quite some difficulties in reducing the gain in the stage. The...
  17. walker1

    Gel cells in parallel ?

    One of my colleauges has assembled a small device that is using 12V from two 12V, 1.2 AH gel cells in parallel. He claims that it had worked fine for 7 hours in the lab, but today it died twice each after about 30 minutes in the field. I myself do hold a little suspicion againt that...
  18. walker1

    Adaptive range tracking

    This was first posted under the "Signal Processing" group yesterday, but not much seems to go on there :-( I am working on a range tracker for a scientific radar. I have tried a full kalman filter and found, that it performed fairly well, as long as the tracked object did not change dynamics...
  19. walker1

    Have coil, need core data

    I have found a ready made, all glued up 170uH coil of unknown origin in a box and would like to use it in a buck switch mode converter. The output current need to be 7-10A, so 170 uH should be more than enough. (50uH has been found acceptable elsewhere) However, I am not sure the coil can cope...
  20. walker1

    Single ended 50MHz sine to square wave

    We need to convert a 50MHz sinewave (maybe 1Vpp) from a built in synthesizer to a 3.3 V clock signal to be used in our logic on another board in the other end of the box. The 50MHz sine will most likely come in a shielded coax cable with ground. We 1st thought about using a comparator, but we...

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