Cool projects to do

[Visitor]

Nice work!

You might want to shift the cap and power input pads to the right to provide some clearance around the mounting hole.

The labels for power and the sensor should be on the top silkscreen layer rather than on the copper layer.

 

[Daniel Gerhard]

Thx

 

[Nigel Goodwin]

any other suggestions would be much appreciated

Only a VERY minor 'mention' - I don't know if you were thinking of soldering the sensor to the PCB or not?, but if you were you should consider that the heat from the processor will affect the readings. Move the sensor off the board on wires, perhaps even with a plug and socket.

 

[Daniel Gerhard]

Only a VERY minor 'mention' - I don't know if you were thinking of soldering the sensor to the PCB or not?, but if you were you should consider that the heat from the processor will affect the readings. Move the sensor off the board on wires, perhaps even with a plug and socket.

How about some female headers i could solder onto the board?

 

[gophert]

And put a capacitor across the power rails of your sensor.

if you plan to run this off battery power and use the deep sleep function of the ESP32, , then you'll want to be able to power down the sensor as well. You can add an "enable" transistor and power the sensor through the transistor. A high side PNP will be a good choice and pull the emitter low to enable power to the sensor. Make sure you add a resistor between the IO pin that will turn the sensor on and the emitter of the PNP.

finally, if you plan to hand-solder the esp32, make sure the solder pads on your pcb extend out far enough to easily get solder onto the PCB and the castellated holes of the ESP32. Some stock footprints are only suited for solder past and reflow ovens and don't leave room for hand soldering.

 

[Nigel Goodwin]

How about some female headers i could solder onto the board?

As long as the sensor is far enough away from any heat from the electronics - and if you build it in a box, the sensor really needs to be outside the box.

 

[Nigel Goodwin]

finally, if you plan to hand-solder the esp32, make sure the solder pads on your pcb extend out far enough to easily get solder onto the PCB and the castellated holes of the ESP32. Some stock footprints are only suited for solder past and reflow ovens and don't leave room for hand soldering.

You're mistaken about what he's using - it's not a bare 'chip', it's a ready built complete module including USB socket for programming, SIL header connections etc.

 

[gophert]

Also, change the outline of the board so there is no board under the esp32 antenna. When it comes to antenna interference, Copper ground planes are really bad, copper traces are pretty bad, a layer of PCB Fiberglas epoxy is kind of bad, and plain air on each side of the board is best - that's how the module was designed so any interference will impact the gigahertz signal.

 

[Daniel Gerhard]

And put a capacitor across the power rails of your sensor.

if you plan to run this off battery power and use the deep sleep function of the ESP32, , then you'll want to be able to power down the sensor as well. You can add an "enable" transistor and power the sensor through the transistor. A high side PNP will be a good choice and pull the emitter low to enable power to the sensor. Make sure you add a resistor between the IO pin that will turn the sensor on and the emitter of the PNP.

Could i not just run the sensor off the power from the esp32?

 

[Daniel Gerhard]

Also, change the outline of the board so there is no board under the esp32 antenna. When it comes to antenna interference, Copper ground planes are really bad, copper traces are pretty bad, a layer of PCB Fiberglas epoxy is kind of bad, and plain air on each side of the board is best - that's how the module was designed so any interference will impact the gigahertz signal.

is that better?

 

[gophert]

Looks great for antenna but not yet perfect for fabrication.

Your board fabricator may (may!) send you a note that they cannot cut inside corners to 90 or to 135 degrees because it is done with a router. You might want to put a 1mm or 0.5mm radius on the four inside corners you created. It is also possible that the fabricator just does it as they wish without informing you.

 

[Nigel Goodwin]

Daniel, there's no need whatsoever for chopping pieces out of the board like that, I can only imagine that Gophert has never seen a Wroom 32?, or indeed any ESP32 device?.

The ESP32 itself comes on a tiny PCB with the aerial etched in the upper surface (so one piece of bare PCB below the aerial) - the Wroom 32 has that board soldered directly on top of a larger PCB, along with the support components (so now two layers of bare PCB below the aerial). So it's completely irrelevent that you're then mounting that above a third bare PCB (although I would advise NOT having a ground plain on your board, just bare PCB) - and presumably you will be mounting it well above the PCB as well? - it's usual to fit PCB headers on the Wroom 32 (they are usually supplied with it) and the corresponding sockets on the PCB below - this allows you to plug and unplug the module as required.

 

[Daniel Gerhard]

(although I would advise NOT having a ground plain on your board, just bare PCB) - and presumably you will be mounting it well above the PCB as well? - it's usual to fit PCB headers on the Wroom 32 (they are usually supplied with it) and the corresponding sockets on the PCB below - this allows you to plug and unplug the module as required.

Hi, I have removed the hole underneath the areal as i think you are probably right, however, just to be sure I have kept the other pcb design, just wondering what you meant by ground plain? And when you say sockets, you do mean something like- soldering female headers to the pcb and male headers to the esp32 so they can be slotted in and out with easy, right?
Thanks for the advice
Daniel

 

[Daniel Gerhard]

Also just wanted to be 100% sure, is 3.7v enough to power the esp32 via vin?
Thanks
Daniel

 

[gophert]

First, there are many develoevelopment boards on the market where esp32 Vroom modules (from eapressif) are soldered to a PCB with USB connectors and voltage regulator and usb to serial converter. Many different companies across china are building them. Many boards work fine but some have terrible range or run at higher amperage than others.

If you look closely, however, the development board made by espressif (a Vroom module on a larger PCB with the other necessary components to simplify development), the Espressif board has nothing below the antenna. That is because Espressif knew how to design the antenna and knows what happens to range and efficiency when there is interference on the antenna. See image on link below.

https://www.mouser.com/ProductDetail/Espressif-Systems/ESP32-DevKitC-32D?qs=%252BEew9%252B0nqrDsObWEpDx6YQ%3D%3D&gclid=Cj0KCQiA48j9BRC-ARIsAMQu3WQFSK-W7j1X-2H05LpR0FuUnPdR3EcLHTTP6y4wyi83Ip3PNmJXQqYaAh9OEALw_wcB

 

[Nigel Goodwin]

Also just wanted to be 100% sure, is 3.7v enough to power the esp32 via vin?

It runs at 3.3V, via it's own 3.3V regulator, so you provide more than that to the Vin pin, and the board provides 3.3V out on it's 3.3V pin.

A Li-Ion (3.7V - 4.2V) is perfectly fine for running the board, and what I often use.

 

[RealGsJR0M3]

Yo ... Fellow rookie here ... I would go for a simple up counter using 555 timer for clocking & JK flip flops ... Then when you have a grasp of what's going on ... Try making a digital clock ... That's what I am planning on doing soon ... My lecturer says "whatever you do enjoy it" ... And don't forget to take your time reading the data sheet (Electrical characteristics) ... Big trap for us young players ... Bonus tip: never build projects you can't use practically

 

[Visitor]

Since nobody has answered about ground planes:

When you have a circuit board fabricated, it's usually 2 (or more) layers. For a 2-layer board, there can be traces on both sides of the board.

Actually, let's start with all the layers on a board.

——— top silkscreen (labels, component outlines)
——— top soldermask (layer that gives the brd color*)
——— top copper (copper tracks)
===== board (circuit board core**)
——— bottom copper
——— bottom soldermask
——— bottom silkscreen

* And prevents solder from sticking where it's not wanted. This layer is built automatically by the layout software.

** Usually fiberglass, but other materials are used too.

The top and bottom layers can be bridged together with vias, which are small holes with plated sides to connect a track through the board.

The fab house process is designed to make 2 layer boards. If you only put tracks on one side of the board, it will still be processed as a two layer board.

So you have the potential for copper on both sides of the board. Often, a ground plane is used on the bottom layer. The ground plane will connect all of the points that are common, usually to the negative power supply. This includes your negative power input terminal, a number of pins on the ESP32 module, and (probably) your sensor common terminal.

You can still use the bottom plane to route traces where you can't make connections on the top layer (where 2 traces must cross to get where you're going), and the layout software will provide clearance between any traces on the bottom layer and the ground plane.

The only thing you must be careful about – whatever traces you run in the bottom layer must allow all of the ground plane to be connected. You don't want floating islands not connected together.

 

[Daniel Gerhard]

Yo ... Fellow rookie here ... I would go for a simple up counter using 555 timer for clocking & JK flip flops ... Then when you have a grasp of what's going on ... Try making a digital clock ... That's what I am planning on doing soon ... My lecturer says "whatever you do enjoy it" ... And don't forget to take your time reading the data sheet (Electrical characteristics) ... Big trap for us young players ... Bonus tip: never build projects you can't use practically

Hi sounds like a great project and will try it out after this one. Just wondering what a JK flip flop is as I have scoured the internet and nothing on the internet makes sense?
Thanks
Daniel

 

[throbscottle]

A J-K flip flop is like an S-R flip-flop but it has some extra gates built in which force it to avoid illegal conditions.