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Pico Prototyping - Building a "Pico Uno"

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Ron
 Ron
(@zander)
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@tracecom I have not heard of the 1117 surge issue. Since I have a few of those I am interested to hear your test results. I use an LM2596 BUCK converter to get 12V down to about 7V to 8V then a 5V LMS1117 to get that down to 5V for 5V logic, or BUCK down to 5V then use a 3V LMS117 for 3V logic. You can see how a dual 5V and 3.3V setup is also possible. Depending on power needs, 5V feeding 3.3V or a second buck, one for each LVR.

The reason for the two step shuffle is that the BUCK is more efficient and produces very little heat while the LVR is precise but at the expense of efficiency losses expressed as heat. I think Bill's video will explain much better than I.

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.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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Ron
 Ron
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@tracecom IIRC, the 1117 is rated at 800ma. I am VERY rusty on this stuff, but isn't that what a capacitor is for? It soaks up the surge. Someone more knowledgeable than me can tell you type and size of cap or check the usual sources (google, YT)

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.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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Will
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Posted by: @zander

@tracecom IIRC, the 1117 is rated at 800ma. I am VERY rusty on this stuff, but isn't that what a capacitor is for? It soaks up the surge. Someone more knowledgeable than me can tell you type and size of cap or check the usual sources (google, YT)

I think @Davee would be the best source for tis kind of information (if he's here)

Anything seems possible when you don't know what you're talking about.


   
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Ron
 Ron
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@will I don't see him, but let's try to beat him to it! 22uf? Not sure if that cap is already on chip, or recommendation to add.

Screen Shot 2022 08 05 at 15.25.58

 

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.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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Will
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@zander FYI @tracecom

The third design already includes two capacitors including a 10uF electrolytic across the "regulator". I don't think it should require any more than that, it seems that if that's insufficient then the regulator is the part that needs more consideration.

Anything seems possible when you don't know what you're talking about.


   
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Ron
 Ron
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@will Ah, I didn't look at Bill's circuit. Where is the 2nd cap, I only see a 10uF.

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.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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Will
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@zander 

Look at time frame 31:44 for the Fritzing diagram.

 

Sorry, there's also a ceramic cap across the 3.3V supply.

Anything seems possible when you don't know what you're talking about.


   
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Ron
 Ron
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@will @tracecom I see he already has a C1 and C2 on his PCB. Maybe Charles can elucidate on the 1117 surge issue.

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.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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Ron
 Ron
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@will I see that, but that has nothing to do with the 1117 does it? I pulled the datasheet for the 1117 and there is a diagram that shows 22uF caps on input and output. I am not sure if that is recommended, or built into the chip. In any case, I am a little confused why we might then be adding a 10uF in parallel with a 22uF. I think we really need to hear back from @tracecom for details re surge. Is the surge a 'push' from the 1117 (is that even possible) or a 'pull' from connected circuitry?

I love a good mystery!!!

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.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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Will
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@zander @tracecom

The LMS1117 is linear regulator and having leading and trailing caps is required to help keep the voltage from bobbing up and down. If you check the sample diagrams for a variety of other regulators of the same type, you'll find equivalent circuitry.

I believe that what we really need is trace com's circuit diagram, we haven't seen that yet, have we ?

Anything seems possible when you don't know what you're talking about.


   
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Ron
 Ron
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@will It's supposed to be identical to Bill's other than he used an LMS117 instead of a Mini-360. The pictures of the completed PCB are posted earlier. Does Bill speak to any 'surge' issue? I would think with those caps in place it would be under control.

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.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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(@tracecom)
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RPi Pico Pack Schematic

@will @zander

Here is the schematic. With the exception of the voltage regulator, it is identical to Bill's fritzing diagram, I think.

 

ETA: It's not the voltage regulator that I suspect of surging. My suspicion is that the RPi Pico draws a lot of current when it is first connected to power.


   
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Ron
 Ron
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@tracecom You forgot the diagram but I knew what it was. Any insight into the surge issue, symptoms, theory?

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.
Sure you can learn to be a programmer, it will take the same amount of time for me to learn to be a Doctor.


   
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(@tracecom)
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@zander See my last post.


   
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Will
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Posted by: @tracecom

 @will @zander

Here is the schematic. With the exception of the voltage regulator, it is identical to Bill's fritzing diagram, I think.

Well, there's your problem. I'm pretty sure that you can't just pop in a linear voltage regulator to replace a buck regulator.

For instance, just check to the sample circuit needed to make the LMS1117 work in the first place.

Anything seems possible when you don't know what you're talking about.


   
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