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paulpthcom

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Everything posted by paulpthcom

  1. Well going to try these, hopefully they work and pretty sure I can solder in the 1210 case in the 0805 pads without problems. If that fails I'll either try the Murata or just try a different chip altogether. Thanks for the help, I'm pretty confused on this one too.
  2. And there we go, just tried a 4.7uH PTH from my parts drawer and it starts up properly with the load as low as 1.0V. So seems to me that even the 600mA 4.7uH SMDs just wasn't enough. Time to go back to digikey and see if I can find something that can handle even more current, though I'm pretty sure that means going up in package size.
  3. The board is super tiny, everything is close to everything else. Just tried out an experiment, I rigger up a 22uH PTH and everything is working much better. As long as the startup voltage is >= 2.0 it output 3.3 with the load. Without the load it can startup at ~1.1V. So either my other inductors were too small or their current rating was too low. Will try some more PTHs to see what happens...
  4. Soldered up another one of the boards and still seeing the same weird behavior. One thing I noticed is if I start without the resistor load and then add it, things seem to behave as expected. Really odd behavior all around. I've included the super simple schematic I had built, maybe someone can spot something stupid I'm missing, but otherwise I'm out of ideas.
  5. I'm using this but when I bought it was labeled Mastech. Works well enough and was cheap, only complain is I wish the fan was quieter.
  6. They are 10uF ceramics, just a 1-2K resistor between output and ground. I don't think there's any shorts anywhere but I think I'm going to solder up another board just to make sure none of the parts have released their magic smoke without me realizing it.
  7. OK so now with the new 4.7uH inductor I get more weird behavior. From 1.0-1.5 V in I get 3.3 V out, from 1.7-2.7 V in I get around 3.0-2.7 V out. The new 10uH inductor just doesn't work at all, the output voltage stays in the mOHM range and the current just gets higher and higher as I crank up the input voltage (up to 500 mA). I'm confused.
  8. Well live and learn and resolder. Maybe I'll get lucky and digikey will deliver the goodies tomorrow so I can try again. I'd like to say I'll read the datasheet more carefully next time but I'd probably be lying. ;-)
  9. I ordered up some 4.7uH and 10uH inductors from digikey with beefier max and saturation current ratings. Hopefully that's enough to get this behaving properly. Thanks for pointing out the importance of high current rating on these.
  10. I switched over to a different 10uH inductor and found the following behavior. If I ramp up my power supply from a low voltage the output voltage stays at around 1.5Vs and starts using more and more current, up to 300mA. Once I hit ~2.1V the output jumps to 3.3V and the current usage drops to < 10mA. I can then ramp down my input voltage to .8V and the output stays at 3.3v. I'm sure there's some logical explanation for this, will read over the datasheet to see what's what, but hey at least it all is somewhat working.
  11. 400+ mA saturation current, not "max DC current"? I wish the datasheet had been a bit more explicit about this... Got a link handy to the one you use?
  12. I believe its http://www.yuden.co.jp/ut/product/category/inductor/CKS21254R7M-T.pdf but not 100% sure, says 130mA as the rated current. I also have tried a 10uH http://www.digikey.com/product-detail/en/MLZ2012N100L/445-6762-2-ND/2523500, saturation current 110mA with the same results. Source power supply is just one of those Chinese linear mode bench supplies.
  13. I must be missing something really basic, but I have a TPS61221 hooked up with a reference schematic, 10uF Input and Output caps and a 4.7uH inductor. With no load I get a 3.3 output voltage as expected. I hook up a simple 1k resistor load and the output voltage drops to ~2.2 volts. Anyone know what I'm doing wrong?
  14. Tested out the PA+LNA module. Seems to work down to about 1.8-1.9 volts. In power down mode it + the 2452 I'm using consume about 1.6uA vs 0.9uA for the non PA+LNA module. Both of these are actually much better than I had expected. Not really sure how to go about getting a good measurement of peak transmit current, but setting my multimeter to store 1k readings and scrolling through them the max I saw was around 50mA. Still waiting to get a couple more sets so I can try both the RX and TX using one and see if it makes enough of a difference in my application to work.
  15. So I'll start up by admitting this is horrible code, you probably shouldn't use it and it's just generally a bad idea, but someone might find it useful. I'm targeting a 2452 without hardware UART and wanted to be able to printf solely for debugging purposes. I know that there's at least one implementation that uses Timer A and T0.1 to implement a soft UART. That version is much more bullet proof and if you actually need to get every last byte you should use that, or better yet a chip with a hardware UART. That being said I only need this for debugging and can miss a character once in a whi
  16. Yeah I figured I'd try measuring with a button and a separate line, though I like your single channel technique better. I was mostly asking about measuring from a timer interrupt because I didn't know if there was some hidden delay of that vs an external IO interrupt. But sounds like even if there is a difference its very small and likely just would get lost in the noise.
  17. Are you saying interrupts and peripherals on the EFM32 are harder to setup than on the STM32? The STM32 is pretty brutal, would hate to think it gets worse. Also how do you measure exact times of going from LMP3->active on the MSP430 when waking up from the timer?
  18. I ordered up a couple more of the PA+LNA so I can at least compare distance of having RX and TX using the PA+LNA vs one or the other. Maybe I'll also try to hack something up to see if the channels really do make any kind of difference.
  19. I just tried out the PA+LNA as the transmitter (instead of receiver) and that does give me the extra range I need. Didn't try it before because the specs claim it needed 3-3.6V, but seems to be running at under 2.5 currently. Going to try to measure exact values of current usage to see where else the specs are wrong. Maybe I can just use some of these modules instead of any repeater stuff.
  20. Yeah I'll likely have to add a repeater or two, but just surprised/disappointed that neither the PA+LNA nor the SMA antenna models seem to make any difference at all in the range.
  21. I'm still playing around with the nrf24l01+ and was wondering if there were any tricks to increasing the distance? I'm running at 250kHZ mode and have tried the following combinations. Chip antenna Master <-> Chip antenna Slave SMA antenna Master <-> SMA antenna Slave PA+LNA SMA antenna Master <-> SMA antenna Slave The problem is none of these seem to get any more distance than the others. I was hoping that the PA+LNA master would give me at least another wall + 10 feet, but it seems to stop receiving at the exact same spot as the others.
  22. Why do you think consider it bad? It seems very similar to how the ti/gcc headers are setup, I mean I'd obviously rather have it defined there and magic numbers in general kind of suck, just don't see why a struct is necessarily any better.
  23. My value is multiplied by 100 to not lose those extra bit of (arguably meaningless data). i believe the formulas are more or less the same from a purely mathematical standpoint, but @@oPossum's is likely faster because it's far more optimized.
  24. You might also want to try without the first line, just use ADC10MEM and see if you get slightly better results that way. I just realized that the readings are probably values from the ADC, so likely don't need the offset/gain factors. Going to try that myself in a bit. @@yyrkoon I believe the error is around +/- 3 degrees C, which IMO is certainly good enough to get a good feel for what the temperature is.
  25. A thermistor seems like a good choice if you need a bit more accuracy than the die sensor, it's cheap, very low power and very easy to drive. I'm using it in a few places where I want to measure the temperature separately from the board.
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