Temperature of PROPMINI..

Probably a question for the designer of the PROPMINI. But, with the 3.3 volt and the 5 volt regulator on the board, and the input voltage between 6.5 and 12 volts, I was wondering what the maximum board temperature would be. Temperature is taken with an infered heat gun. I do know the temperature will vary depending on the input voltage. Higher temperature with the higher input voltage, I understand. Also, I know it depends on what else I am running on the 3.3volt and 5 volt supplies of the PROPMINI. The thermostat that I designed in another thread, with photos, draws about 190 mA's.

With about 11 volts in, I was running a board temperature of 130 degrees F. Dropping the input voltage to 6 volts, reduced the board temperature to about 90 degrees.

Any thoughts from the designers of the PROPMINI, or anyone in the know...about the maximum board temperature.

Thank you...DenO

Comments

  • Duane DegnDuane Degn Posts: 10,348
    edited 2020-11-18 - 21:47:09
    The temperature is going to depend on how fast you can move the heat away.

    I'm pretty sure the PropMini uses linear regulators so it drops the voltage by converting it to heat.
    If you assume the 3.3V regulator uses all the 190mA then you need to get rid of about one and a half Watts of heat.

    With a lot of air flow, the temperature would likely be not much above ambient. With no air flow, it could probably get hot enough to shut itself off.

    You might want to think of adding a switching regulator so you don't have to get rid of as much heat. You could either drop the 11V to 6.5V using a switching regulator. If you don't need super clean 5V power, you could bypass the 5V regulator and use a 5V switching regulator for you 5V needs.

    It's pretty common in Propeller projects for people to use a switching regulator for the 5V line but then use a linear regulator for the 3.3V line. Linear regulators tend to be quiet compared with switching regulators.
  • Just wondering if you can load a program into the propmini using only the propplug and not have any Vin? Just not sure, because when I try to do that, seems like the RAM might load but not the EEPROM..
    Any thoughts and thank you again..deno
  • Duane DegnDuane Degn Posts: 10,348
    edited 2020-11-26 - 14:30:23
    The PropPlug doesn't have a power pin. There are some USB to serial devices which include 5V and/or 3.3V power pin but you need a way to get this power to PropMini.

    When I make my own PCBs which include a PropPlug interface, I add an extra pin next to the ground pin to allow the board to be powered from USB. "VCC" is 5V on this device (there is a 3.3V regulator on the bottom of my PCB).

    NonaProp141201d.jpg

    You could probably use the USB to serial shown in the photo to power the PropMini. I think connecting to the 5V line, from the USB to serial PCB, to the PropMini's 5V line would provide enough power for the PropMini.

    Some of these other USB to serial devices require a capacitor in series on the DTR line. On some devices the reset doesn't trigger correctly without the extra capacitor in series. The board in the photo includes this capacitor. The capacitor may be bypassed with a jumper when using a normal PropPlug or other device which doesn't need the capacitor.



  • Beware, the 3V3 from these plugs cannot power a prop board as there is not enough current!
  • Cluso99 wrote: »
    Beware, the 3V3 from these plugs cannot power a prop board as there is not enough current!

    Do you mean not enough juice for powering an application and talking to the chip or just for programming only ? The former is quite clear, the later - I'm not so sure.
  • For neither, I think. The 3V3 is generated from a really tiny volatage regulator, I think the FTDI ones are specced for 75mA. If there's a 5V pin it's generally connected straight through and you can draw 750mA (minus whatever the serial itself would need). That's still not a lot though. You can draw significantly more when the USB is connected to a powered hub or a phone charger (usually at least 1.5A)
  • Cluso99 wrote: »
    Beware, the 3V3 from these plugs cannot power a prop board as there is not enough current!

    I think this depends on the device used. I generally use the 5V from the USB and use my own 3.3V regulator (on the bottom of the PCB in the above photo). However I think some USB to serial devices can provide enough current for modest Propeller applications. Apparently the CP2102 can source 100mA of current on the 3.3V output.

    Cp2102VReg.PNG

    Some USB to serial devices (like the one in the earlier photo) include a solder jumper to allow one to use either 5V or 3.3V on the VCC pin.
    1231 x 892 - 402K
  • Cluso99Cluso99 Posts: 16,951
    edited 2020-11-26 - 23:25:24
    The 3V3 regulator is internal to the USB chip and also powers the USB chip. There is generally not enough current left for anything else other than perhaps leds. Not all chips are real CP2102 or FT232 as there seems to be lots of clones.
    Your choice, but be warned.
  • jmgjmg Posts: 14,541
    denno wrote: »
    Just wondering if you can load a program into the propmini using only the propplug and not have any Vin? Just not sure, because when I try to do that, seems like the RAM might load but not the EEPROM..
    Any thoughts and thank you again..deno

    Are you talking about programming the EEPROM on a test bench, and using another power source in an end product ?
    The Prop1 data has Icc curves and data, and you should be fine programming EEPROM, using a lower current power source than would be needed to run all cogs at 80MHz

    P1-reading-EEPROM currents indicate about 2.4mA and additional write currents needed by EEPROM itself are 3~5mA ballpark MAX specs


    Regulators are quite cheap, and ones with Power-GOOD are becoming more common, so you are better to spread hings thermally and use a PG regulator in a final product design.
  • It would appear that using the USB port to power the propplug (pictured below) will download to RAM, but times out to DOWNLOAD THE EEPROM. My PROPPLUG does have the FT232...thanks to all, I believe the question has been answered...and yes, the connecting wires in the photo are configured correctly.
    3072 x 4096 - 4M
  • denno wrote: »
    It would appear that using the USB port to power the propplug (pictured below) will download to RAM, but times out to DOWNLOAD THE EEPROM.

    That is so odd. The Propeller is receiving all its power from the data pins.
    I'm not sure, but I have a hard time believing powering the PropMini this way is good for PropPlug. It might not be good for the Propeller chip as well since all the power is is being supplied through the I/O rather than power pins. The Propeller chip is sensitive to how it is powered. It's not very hard to blow the PLL circuit on the chip (I've done so many times).

  • denno wrote: »
    It would appear that using the USB port to power the propplug (pictured below) will download to RAM, but times out to DOWNLOAD THE EEPROM. My PROPPLUG does have the FT232...thanks to all, I believe the question has been answered...and yes, the connecting wires in the photo are configured correctly.
    IF the photo is your setup, then you don't have 5V connected to your prop board so you are not powering it. It is a wonder you can even download any code!
  • Perhaps i'm not downloading any code after all. In propbasic the download page goes by real fast, then clears that page and then back to the program page.

    Cluso99..you are correct, as the download times out on loading the RAM not the EEPROM. As soon as i supply 5volts to Vin on the propmini, the download completes.
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