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433 Mhz cap recommended in 'Using Inexpensive 433 MHz RF Modules with Arduino' 4 yrs ago

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(@pratto20)
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In a pinned comment it was suggested that a 100 uf capacitor be installed. It didn't say what kind.

My only 100 uf capacitors are big electrolytic clunkers. I am wondering two things :

Does the cap need to be electrolytic ?

What is the tolerance for size ?

 

  


   
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Ron
 Ron
(@zander)
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@pratto20 I am not sure what a pinned comment is. can you post the post link?

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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(@pratto20)
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@zander  Maybe I'm using the wrong term. Just below the video, in the comments section is the comment i'm referring to. it seems to have some precedence or importance. but whether it's pinned or not, my question remains.


   
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Ron
 Ron
(@zander)
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@pratto20 I still don't know to what you are referring. I am including a screen print, the post ink is the icon bottom right. Goto the post that is causing you a problem and click it's post link.

Screen Shot 2022 06 07 at 06.01.41

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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frogandtoad
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@zander

Posted by: @zander

@pratto20 I still don't know to what you are referring. I am including a screen print, the post ink is the icon bottom right. Goto the post that is causing you a problem and click it's post link.

Screen Shot 2022 06 07 at 06.01.41

On Bill's YT video, there is a viewer comment that recommends using the cap, though the comment doesn't specify what type of cap to use.  Having said that, I think an electrolytic is fine, as long as it covers the voltage it is being applied across and not too large.


   
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Ron
 Ron
(@zander)
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@frogandtoad Glad you could help, I still have no idea what he is referring to but now it doesn't matter, thanks.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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frogandtoad
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@zander

Posted by: @zander

@frogandtoad Glad you could help, I still have no idea what he is referring to but now it doesn't matter, thanks.

I'm guessing, but I think he's referring to this comment:

image

Cheers


   
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(@pratto20)
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Yes. thanks. that is what I was referring to. I had just made a screen shot showing the same thing.

I was so new to the drone bot workshop that I thought that the comment was from bill (I didn't know his name), and that he put it in a prominent location (pinned to the top).

I ordered a smaller (in physical size) 100 uf, bi polar electrolytic cap. I haven't noticed any better performance with it in or out, but what do I know ?


   
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(@davee)
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Hi @pratto20

I ordered a smaller (in physical size) 100 uf, bi polar electrolytic cap. I haven't noticed any better performance with it in or out, but what do I know ?

For many low power circuits, a polarised electrolytic capacitor, with voltage rating a bit higher than the maximum expected rail voltage, connected the correct way round, should be fine for decoupling. Sometimes a smaller ceramic of 10nF to 100nF, is also added in parallel to provide support at higher frequencies, as electrolytics performance at high frequency is rather poor.

Decoupling capacitors are essential for most circuits to ensure the active devices 'see' a stable supply of power ... however, many circuits will tolerate a certain amount of 'instability' in the power supply, so that a circuit may work satisfactorily for long periods of time with inadequate decoupling ... however, inadequately deoupled circuits are liable to 'misbehave' at any time. For example, battery powered audio devices such as radios may tend to start make poping noises, known as motor boating, as the battery becomes discharged.

Hence, it is not unusual to find adding a decoupling capacitor makes no apparent change to a circuit .... but failing to provide enough decoupling can result in a circuit that fails at the most annoying moments.

Best wishes, Dave


   
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(@pratto20)
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@davee  Hmmm. I have been having weird, intermittent, error messages while running my arduino sketch, and failure to load at other times. The sketches ran fine the night before, or just 10 minutes ago, but now not.

The only solution I've found is saving the sketch with the uploading error as a different name, not saving it as itself, exiting the IDE and powering down the computer. wait. re-boot. back in the IDE, select the sketch that i was running when the error occurred (but didn't save), load it and it runs. What a pain, and a mystery.

I do have the de-coupling cap next to the 433 MHz receiver. Maybe I need one beside my MEGA too.

thanks for your help.

 


   
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frogandtoad
(@frogandtoad)
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@davee 

Posted by: @davee

[snip]

Hence, it is not unusual to find adding a decoupling capacitor makes no apparent change to a circuit .... but failing to provide enough decoupling can result in a circuit that fails at the most annoying moments.

Nice explanation.... that's why you're the hardware guy 😉

Cheers


   
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(@davee)
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Hi @pratto20,

  Your problems might be associated with the Arduino IDE ... others on this forum have vastly more experience in this area than me, but I don't think I am alone in sometimes finding the loop of events:

compile/link --> download program to Arduino --> run program on Arduino, viewing on Serial Monitor --> edit program and loop back to compile/link

gets in a bit of a tangle ... usually either refusing to download, or not connecting to the serial monitor

The system relies on using the same USB connection for both program download and serial monitor, which means code at both the PC and the Arduino ends must be 'in sync' with each other. Having to run in different configurations for each of the steps, using the same single USB cable can result in the ends 'thinking' they are at different parts of the loop.

I am not sure if there is a definitive cure for this .. I usually resort to unplugging and reconnecting the USB and trying again... occasionally I even reboot the PC, as I suspect USB device driver or IDE code in the PC may lose the plot.

Others might like to comment and improve on my primitive methods.

-----

As for extra decoupling to Arduino, that is a possibility, though generally they seem to be reasonably 'solid' in this respect. Decoupling is one of those areas where the 'unexpected' is the 'expected result'. So when in doubt, try it!

When powering the Arduino via the USB socket, both the USB cable, and the power source (usually the PC) can be 'flaky'. From my limited experience, Arduinos can usually cope, provided they are not connected to large external loads, but the ESP8266 and ESP32 boards are often reported to be improved by some extra decoupling.

Of course, many of the boards you can buy through Amazon, etc. are produced by small production houses who 'blindly' copy someone else's design, and regard showing the board can run 'blinky' or similar for two seconds, as a comprehensive design and production test. Thus each board is a bit like a lottery ticket .. but on the positive side, many are near to the price of a lottery ticket.

Best wishes, Dave


   
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Inst-Tech
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Posted by: @frogandtoad

@davee 

Posted by: @davee

[snip]

Hence, it is not unusual to find adding a decoupling capacitor makes no apparent change to a circuit .... but failing to provide enough decoupling can result in a circuit that fails at the most annoying moments.

Nice explanation.... that's why you're the hardware guy 😉

Cheers

Yep.. @DaveE is right on the money..The problem with hardware design is that components are not always within their tolerance and specifications. Especially electrolytic capacitors..  over voltage, connecting them incorrectly, and age take their toll on these devices, and other components as well.  When I can, I prefer ceramic type (MCLL) or disc types, although they generally have a much lower capacitance range than electrolytic, (typically between 1nF and 1µF, although values up to 100µF are possible.)  Electrolytics can leak over time and damage your board tracings,  are more sensitive to over voltage and temperature variations, and because they are polarized, must be correctly connected.. Ceramics are better suited to circuits with high frequency, such as what  @pratto20 is working with..since they are smaller in size, you can add a few in parallel to increase capacitance.. well that's my 2-cents worth.. Good luck with your project

Regards,

LouisR

 

LouisR


   
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Ron
 Ron
(@zander)
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@pratto20 Let's start by removing the capacitors and trying again. I am 99.99999% sure that is NOT the problem but it is the last thing you changed before it started to fail. All that nonsense re renaming and rebooting is noise. Stop doing that and let's find the real error.

Start at the beginning and take a screenshot of the first error message. As far as failures to load that is not unusual, I have days where that happens every few uploads. I just try again BUT I also make sure the serial monitor has been terminated as that is normally the problem.

First computer 1959. Retired from my own computer company 2004.
Hardware - Expert in 1401, and 360, fairly knowledge in PC plus numerous MPU's and MCU's
Major Languages - Machine language, 360 Macro Assembler, Intel Assembler, PL/I and PL1, Pascal, Basic, C plus numerous job control and scripting languages.
My personal scorecard is now 1 PC hardware fix (circa 1982), 1 open source fix (at age 82), and 2 zero day bugs in a major OS.


   
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(@pratto20)
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@davee  thanks. i'll mull that over.


   
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