Search results

  1. K

    First resonate a short antenna, then impedance match it ?

    Or incorporate the reactive resonator component (one capacitor or one inductor) into the impedance matching network, any difference besides lower component count ?
  2. K

    Long differential pair to balanced antenna

    Hello, If I understand correctly, a differential PCB trace pair feeding a balanced antenna will not radiate much. Of course, there will be no ground plane above or below the diff pair. So then the antenna's radiation pattern will also not suffer much ? Can the diff pair + antenna piece...
  3. K

    Cause for TX frequency difference

    i have an ISM band transmitter device based on the MAX41460 chip. It expects a 16Mhz, 12 pF crystal. Switched from set A of parts: - crystal: https://www.tme.eu/ro/en/details/16.00m-smdxt224/smd-quartz-crystals/yic/ - PCB antenna feed inductor...
  4. K

    thermal issues: surface mounted on 1" x 1" FR4 board

    A number of parts are rated at certain thermal impedance with a note, something along the lines of like in this datasheet for instance - https://www.tme.eu/Document/8ae9fea82a7cb44d4c881a980e95a2fe/siss05dn.pdf Does this mean that in order to achieve the stated thermal impedance (63C/W in this...
  5. K

    Automotive ISO 7637-2 transients dealt with by MCU ?

    The ISO is talking about +150V / -220V fast transients. Aside from these, there is also the dreaded load dump 400 ms, 79V and 0.5 ohm Does this design stand a chance to protect a large resistive load drawing up to 10A ? Q1, Q2 = 250V N channel MOSFETs Q3 = logic level N MOSFET D1 = standard...
  6. K

    Swapping diode for P-MOSFET: reverse spike protection

    How do I replace D2 in this answer with a P-MOS FET ? I am thinking about this diagram: The two D1 symbols are just one bidirectional TVS diode (missing symbol in circuitlab) with Vcl_max = 24.4V and M1 has Vgs_th = -4V Vgs_max = -20V. Vds_max - should I worry about it ? Will this protect...
  7. K

    How will a car 10A circuit deal with double load?

    The brake lamp circuit is generally fused at 10A on most passenger cars. Since incandescent light bulbs present inrush currents of about 10x their steady state currents, I am guessing these fuses are slow fuses. One such bulb will steadily draw 1.5 - 2A. I am looking to using that same circuit...
  8. K

    Naughty circuit breaker situation

    Happy new year all! Ever since I had put in a WiFi controlled relay at a led light outside, trouble has begun... My setup: It was on a Christmas day, family was waiting for me, I think I... have not made very good contacts at WR in the diagram above :-) - Few days after CB0 started...
  9. K

    EP5R marking

    second line reads HAC I think it is a MEMS sensor of some sort, LGA package. Couldn't find it through online part search engines... if someone knows of it, please tell. Thanks
  10. K

    crystal, oscillator problem ?

    Working with this radio transmitter MAX41460. It is supposed to output a signal on its CLKOUT pin for the MCU to interrupt on and shift out radio bits. It works fine when MCU (ATTiny88) runs at 2 or 4 MHz from its internal RC oscillator, but that is too slow for the workload. 8 MHz would be...
  11. K

    this evil I2C monster scoffing at me from its minute package

    It is this little guy - a MEMS sensor in its WLP-4 package. Setup: - Arduino Uno R3 - some 30 cm of wires - home etched breakboards for the culprit sensor (two of them) - Logic level shifter 5V - 3.3V: My mosfet is 2N7000 with 9k1 pullups. Works just fine for SPI, this being its first go...
  12. K

    LGA / MEMS / magnetic sensors - why do I see them fail so much ?

    i know these kind of sensors are sensitive but, man... how do they fail so easily ?! My procedure: - bake the MEMS sensors @ 125 deg C for 9 hours (dry out phase) - apply solder paste over the boards through an electropolished stencil - place the sensors by hand as straight as I can then put...
  13. K

    tens of years battery life ?

    The device is a I2C transmitter + AVR 8bit MCU. It transmits for about 10 ms @ 10 mA every 20 minutes or so. The rest of the time I set up the MCU in sleep mode drawing some 4 uA. My calculations for 2xAA alkalines, useful voltage range 1.8 - 3.2 V (considered 2200 mAh as useful capacity), at...
  14. K

    Led driver of constant current - is it really constant ?

    I have never used led drivers and after some good hours of searching I am still at loss. In the specific case of the ZXSC380FHTA led driver, will the current be constant at the output and if it will be, to what value ? It says that
  15. K

    gyroscope (un)desired traits for the extended kalman filter

    Am i wrong to assume that an undesired characteristic of such an instrument is "high vibration rejection" ? As far as I understand, EKF needs to sense its environment as good as it can in order to output an accurate state estimation. I am looking for just one axis attitude should it matter, and...
  16. K

    Green 1206 sized "TH" marked parts

    Does anybody know what these two are ?
  17. K

    Artifact-less ISM band radio transmitter part

    I have tried a couple of FSK/OOK wide frequency range transmitters (among the lines of 100 - 1000 MHz) at 433.92 MHz. They both produce artifacts; i.e. extraneous signals in front and / or after the desired signal - in either OOK or FSK modes. I am sure there are some parts out there that are...
  18. K

    Heater thermsotat receiver unit

    Hello, my central heating would not start / stop every time the transmitter thermostat would issue a start / stop command, but only some of the time. Took the receiver apart, found the film cap (yellow) next to the output relay to be off by a big factor (200 nF measured / 560 nF nominal) and...
  19. K

    Have I killed the MCU for good ?

    by, maybe, grounding a HIGH output ? I have a PCB with an Atmega88PA MCU and an ADS114S06 ADC that both share three SPI lines (SCK, MISO, MOSI). I was trying to program the MCU (via SPI interface), it responded with its device signature OK, but then verifying the flashed program would fail on...
  20. K

    weird DMM voltage readings

    Hello, I am trying to debug some PCB - the LED below won't light up Took ut my trusty DMM and measured V_AC = 3.31 V V_BC = 1.33 V V_AB = 0 V <--- ?? should it not be around 2 V ? Thanks!
Top