Newbie at PCB layout. Want to make sure I am not making any obvious mistakes.

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dcbingaman

Joined Jun 30, 2021
1,065
It has been about 10 years since I last did a PCB layout. Back then I used ExpressPCB for a rather simple board. The following is an attached KiCad project with completed schematic and what I think is a completed board layout. I wanted to get input on if I did everything correctly, is there anything I missed and is this ready to be produced? I feel a little uncomfortable getting PCB's made until I know I have no mistakes. Thanks in advance for anyone's input who happens to use KiCad. This is a hobby project so it is all open source. Anyone else is free to reuse if they want.
 

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dcbingaman

Joined Jun 30, 2021
1,065
When I opened up the sch and PCB files I found only empty files. I am using KiCAD 5.1.10. The files are very small.
That is strange, the directory structure should have looked like this? I am using 5.1.9. Did you try opening the project file KiCad1.pro?
Thanks for your help.

Top1.PNG
 

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ronsimpson

Joined Oct 7, 2019
2,989
In the ZIP the top level looks like this: Every thing is blank. Opened .pro, then tired .sch and .kicad_pcb.
1629316046386.png

Went into the folder and found this: The .PRO will not work for me but the .sch and PCB works. I can not load the libraries for the sch. and don't have time to fix that. The layout looks good. Four layer with power & ground inside.
1629316161498.png
The "HC12_WIRELESSUART" looks interesting. I just down loaded the manual for it.
Can you send a .pdf of the sch so I can see it.

RonS.
 

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dcbingaman

Joined Jun 30, 2021
1,065
Ok. Here I have included the schematic in pdf format along with the gerber files. I think there are multiple online tools for looking at the gerber files.
 

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Thread Starter

dcbingaman

Joined Jun 30, 2021
1,065
In the ZIP the top level looks like this: Every thing is blank. Opened .pro, then tired .sch and .kicad_pcb.
View attachment 245959

Went into the folder and found this: The .PRO will not work for me but the .sch and PCB works. I can not load the libraries for the sch. and don't have time to fix that. The layout looks good. Four layer with power & ground inside.
View attachment 245960
The "HC12_WIRELESSUART" looks interesting. I just down loaded the manual for it.
Can you send a .pdf of the sch so I can see it.

RonS.
Sent pdf in last post. Yes that module is very easy to use. I have experimented around with it some. When I used the 'included' spring antenna it did not have enough range for my requirement. But I found if I replaced that with a straight wire antenna around 8 inches long works for very long range. I use two of them. One talks to the PC via a USB to UART that I simply wired to the transceiver using a simple protoboard. If you do not have power limiting requirements it has very sensitive receiver and good transmitter.
 

ronsimpson

Joined Oct 7, 2019
2,989
I don't see any thing wrong. Will any of the linear regulators run hot? You could use heaver traces on the regulators to pull heat away.

I am thinking about other jobs this board could do. Add a 4 pin connector with I2C, power and ground. Then other boards could be added like a ADC. I am measuring temp in all buildings on the farm but need to know "Sun up/down" (brightness). Would like a wireless "is the door open" sensor. The chickens have heat and fan, temperature but no way to know if the door is open or closed.

Fun project, good job, best of luck. RonS
 

nsaspook

Joined Aug 27, 2009
13,086
I looked at it quickly. Generally I would add a reset switch option pin header for the MCLR signal across C1 and add pin headers for the unused controller GPIO pins if you have plenty of extra board space.
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
1,065
I don't see any thing wrong. Will any of the linear regulators run hot? You could use heaver traces on the regulators to pull heat away.

I am thinking about other jobs this board could do. Add a 4 pin connector with I2C, power and ground. Then other boards could be added like a ADC. I am measuring temp in all buildings on the farm but need to know "Sun up/down" (brightness). Would like a wireless "is the door open" sensor. The chickens have heat and fan, temperature but no way to know if the door is open or closed.

Fun project, good job, best of luck. RonS
Thanks for the input! The max current on the regulator going to the wireless module is 100mA. The max current for the P3.3V is 50mA. Do you think I should run heavier traces for them? The reason for turning the transceiver on and off is to save power. I am using it in a battery operated device that measures temperature every minute and stores it, then the PC downloads the data at the end of the day. If you have access to 120VAC with wall wort power you could simplify it. The microcontroller goes to sleep for one minute, wakes up, turns on the transceiver, takes a temperature measurement stores it. If PC attempts communication during this window then it allows download of all data to PC.
Thanks again. Feel free to use it any way you want to. If you come up with another application, would be nice to see your final design.
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
1,065
I looked at it quickly. Generally I would add a reset switch option pin header for the MCLR signal across C1 and add pin headers for the unused controller GPIO pins if you have plenty of extra board space.
Thanks for looking at it and thanks for the advice.
 

ronsimpson

Joined Oct 7, 2019
2,989
U5. Input near 9V and output 5V. Current 100mA so that 400mW worse case. 9V= full battery or 9V = charging battery??
What is the temp rise for that part?
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
1,065
U5. Input near 9V and output 5V. Current 100mA so that 400mW worse case. 9V= full battery or 9V = charging battery??
What is the temp rise for that part?
Good point. I have a lot of these parts on order. I have a solderless breadboard for proto-checkout along with some SMD to 0.1" on center headers. The maximum battery voltage is 9V. We do get a little break because I have two diodes in series before the regulator. So probably closer to 300mW. That has me a little concerned as well. It is powering the wireless UART. That has the maximum current when transmitting at 100mA. The wireless UART will spend most of it's time off except when downloading data to the PC. This will take about 3 minutes. But it is only transmitting them about 1/2 the time making the average current lower. I can see the current changing on my power supply with my prototype, but it is not giving me the actual instantaneous current. I think I am going to place a small resistance of say 1 ohm to ground and use a scope to measure the drop when it is transmitting so I can get a feel of what the current is doing with respect to time.
I am not at this point sure what the temp rise will be for that part. Is there a way of figuring that out? There is no air movement and the ambient temperature can be below freezing in the winter to over 100F in the summer.
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
1,065
U5. Input near 9V and output 5V. Current 100mA so that 400mW worse case. 9V= full battery or 9V = charging battery??
What is the temp rise for that part?
9V = full battery. This project is using 6 D Cell batteries in series so max is 9V and minimum is going to be around 7V at which point I will replace the batteries with new ones. My calculations show this circuit should run for at least a year or better before needing new batteries. The wireless UART when in data gathering mode turns on for about 1/2 second every minute to check and see if the PC is trying to communicate with it. The microcontroller goes to sleep and wakes up for about 1/2 a second to take a temperature measurement at the same time turns on wireless UART to see if PC is trying to communicate with it.
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
1,065
U5. Input near 9V and output 5V. Current 100mA so that 400mW worse case. 9V= full battery or 9V = charging battery??
What is the temp rise for that part?
I found this in the Linear Regulators datasheet:

LinearRegPower.PNG
I am using the SOT23-5 (This is absolute allowed value, exceeding it could damage the part according to the datasheet)
The hottest I have ever seen it here is 112F or around 44C. According to this graph at 50C the SOT23-5 package can handle no more than 470mW. Do you agree?

Attached as well is the datasheet.
 

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Thread Starter

dcbingaman

Joined Jun 30, 2021
1,065
U5. Input near 9V and output 5V. Current 100mA so that 400mW worse case. 9V= full battery or 9V = charging battery??
What is the temp rise for that part?
According to the datasheet pin 4 is electrically not connected and you can if you want connect it to the output or ground. I currently do not have it connected anywhere. Do you think it would help thermally to connect this pin to the ground plane? The datasheet does not say much about it.
 

ronsimpson

Joined Oct 7, 2019
2,989
package can handle no more than 470mW.
Agree. That puts the die at max temperature. 470mW
It appears the silicon is on the ground pin which holds most of the heat. In the other package it is what is used for heat sinking.

I selected the traces and edited them to 0.6mm. Then did a Zone fill, solid-no thermals, GND. The edited pin 4 and changed the net to GND. This will cool off the part. Some people would add some VIAs under the part (GND) that will pull the heat to the other side of the board. Because you have a wonderful GND layer, it will spread the heat out over a larger area.
1629332777719.png
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
1,065
Agree. That puts the die at max temperature. 470mW
It appears the silicon is on the ground pin which holds most of the heat. In the other package it is what is used for heat sinking.

I selected the traces and edited them to 0.6mm. Then did a Zone fill, solid-no thermals, GND. The edited pin 4 and changed the net to GND. This will cool off the part. Some people would add some VIAs under the part (GND) that will pull the heat to the other side of the board. Because you have a wonderful GND layer, it will spread the heat out over a larger area.
View attachment 245972
Nice! Thanks! I will make these changes and post it.
 

Thread Starter

dcbingaman

Joined Jun 30, 2021
1,065
Agree. That puts the die at max temperature. 470mW
It appears the silicon is on the ground pin which holds most of the heat. In the other package it is what is used for heat sinking.

I selected the traces and edited them to 0.6mm. Then did a Zone fill, solid-no thermals, GND. The edited pin 4 and changed the net to GND. This will cool off the part. Some people would add some VIAs under the part (GND) that will pull the heat to the other side of the board. Because you have a wonderful GND layer, it will spread the heat out over a larger area.
View attachment 245972
I seem to be having trouble creating a fill layer that is under the solder mask. I obviously do not know what I am doing.
 

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Thread Starter

dcbingaman

Joined Jun 30, 2021
1,065
Agree. That puts the die at max temperature. 470mW
It appears the silicon is on the ground pin which holds most of the heat. In the other package it is what is used for heat sinking.

I selected the traces and edited them to 0.6mm. Then did a Zone fill, solid-no thermals, GND. The edited pin 4 and changed the net to GND. This will cool off the part. Some people would add some VIAs under the part (GND) that will pull the heat to the other side of the board. Because you have a wonderful GND layer, it will spread the heat out over a larger area.
View attachment 245972
I will not be in tomorrow. Be back on Friday. Thx
 
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