Search results

  1. K

    tens of years battery life ?

    I think so. Firstly there is 2.2Ah only as the cells are connected in series. Secondly if you divide Ah by A/h (measure units of drain per hour) then the 14 667 is not hours but hours squared. My guess is that the second line it would rather be 0.01 Amper * (0.01 second / 3600 second). Did i...
  2. K

    tens of years battery life ?

    No I have not. I figure still some 20 years will be left. It still seem like a huge service life.
  3. 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...
  4. K

    Led driver of constant current - is it really constant ?

    Thanks a lot Tony! Relearned a few things today (if I ever learned them from school, that is :) )... just one thing I can not grasp on the circuit - what does the 470 pF do ? In my simulation, removing it doesn't cause much difference. And one more - can I replace the first transistor with a...
  5. K

    Led driver of constant current - is it really constant ?

    That's quite an old school piece of work! Unfortunately it won't easily fit into my head. For the second circuit: Something tells me that if I replaced that battery with an alkaline AA cell, the LED will light up from brighter to dimmer as the battery depletes (1.6 -> 0.8 V). Is this the case...
  6. K

    Led driver of constant current - is it really constant ?

    Of course... you are right, back to SMPS. Again. The thing with those SMPS (I am talking about voltage regulators as I was unable to find a suitable led driver for just one 2V led) is the utput voltage problem. Vf varies between 1.6 and 2.4V with the leds I want to use. I guess I could check...
  7. K

    Led driver of constant current - is it really constant ?

    Aha! Still, I am not on the same page as the datasheet. it clearly says Furthermore: Are they not defining I_set as the total current flowing into V+ pin ? Aside from that, if the diode does all the temp compensation, what would the R1/R_set divider purpose be then ? From the picture...
  8. K

    Led driver of constant current - is it really constant ?

    How about this one ? I am confused by this diagram. Would the voltage drop on R_set be 67.7 mV (@ 25 deg C) ? And the voltage across D1 1V perhaps, and then what, how does this work as a zero temperature coefficient current source ? And why are they redefining the V+ current as 2 * I_set when...
  9. K

    Led driver of constant current - is it really constant ?

    Or... Is there a minimum output voltage for the MIC2287 ? Datasheet only specs a max of 34V. Also, is an ~84% efficiency decent or kind of low for these chips ? Looking at the 3 series LEDs @ Vin = 3.0V, 20 mA graph. Judging by the graphs below I am speculating maybe 85% efficiency for just...
  10. K

    Led driver of constant current - is it really constant ?

    Yes, got it. Unfortunately not many led drivers out there that will drive just one led and do it properly. Back to SMPS.
  11. K

    Led driver of constant current - is it really constant ?

    I surely could, less the series resistor which i think not required for a voltage regulator sized at precisely 2V output. Just that it has more parts to solder.
  12. K

    Led driver of constant current - is it really constant ?

    my application is 3.2 V alkaline batteries into a 20 mA @ 2V led
  13. K

    Led driver of constant current - is it really constant ?

    Alright. Then it looks like i'd better go with a switching regulator for constant voltage. Or are the led drivers still a better choice for driving a led at constant current / voltage ?
  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

    Hi, I mean the vibration signal. An instrument advertised as ""high vibration rejection"" will truncate it.
  16. 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...
  17. K

    Green 1206 sized "TH" marked parts

    Does anybody know what these two are ?
  18. K

    Heater thermsotat receiver unit

    None of the 4 x 100 uF caps were anywhere close to 100 uF :confused:. The diodes looked fine. Replaced them, did this and that, still nothing. Now it does not actuate the relay even with help from a probe. The cheapest thing to do right now would be to put together a new PCB and some components...
  19. K

    Heater thermsotat receiver unit

    Hello, I have done some live measurements and I have noticed that for [see second / third pic in the first post]. Q3, V_be = 0.7V, V_bc = 0V - when I touch the base or emitter of this transistor with one of the DMM probes then the relay toggles Q4, V_be = 0.7V, V_bc = 0V - when I touch the...
  20. K

    Artifact-less ISM band radio transmitter part

    Thank you! The separation I wanted is in time, so I guess a passband filter would not do it. Here are two pictures of the artifacts for one of the transmitters: This is a Si4012 transmitter and I already have an answer from Silicon Labs on these artifacts as not being possible to remove...
Top