Phone on a breadbord

Question

My current electronics project is to build a very simple customizable "phone". It is my own idea, with as ultimate goal to learn about microcontrollers and basic electronics.

This is my set-up so far

I managed to interface with the microcontroller, and the voltage transformation circuit seems to works (how do you call this?). The issue is with the Neoway M590 GSM modem. It reboots every couple of seconds. I think this is because the modem draws a peak current when trying to connect to the network a few seconds after starts-up, and automatically shuts down because the voltage drops too low for safe operation. This is why we need the big capacitor there (1000 uF). I power the board with a PSU that can supply more than enough amperage. Communication is via a USB-TTL converter which I connect to a computer.

Please note that in my set-up I have completely eliminated all dependence on the microcontroller and voltage transformation circuit, in an effort to isolate the problem.

The Neoway M590 came with a pre-designed PCB

I have soldered one of these PCBs with a Neoway M590 and had no modem restart issues (after I put in a heavier capacitor).

Answer 1

The problem is quite likely related to your breadboard. They are not very good for high currents.

Why? Well there are a few reasons, but it all comes down to your components not being that well connected.

Firstly you inevitably have a bunch of thin wires going between everything. I highly doubt your average jumper wire is rated for 2A. But even if it is, we still have some other problems.

Then, each of those wires and components are only softly held by the hole in the breadboard. How much surface area of the lead is actually in contact with the conductor? Potentially not very much and this is repeated multiple times along the current path.

Finally there is the path between each hole on the board. We don't know how good that is, but it's also probably not designed for a very high current.

So all these little things are going to add up along the current path and when you finally reach your component, there simply isn't enough power for it.

What can you do? Well you could try re-arranging your breadboard to mitigate the issues. But really you are probably best off just building the PCB and soldering wires to it which you can then connect to your micro-controller on the breadboard.

Answer 2

THese breadboards were invented long before GSM was even thought of nor high speed PIC uC's.

They are not really well-suited for any RF or high transition speed CMOS uC operating with 10ns risetime. Back in the 70's CMOS was slow and putting caps next to each IC usually worked.

However, you have huge loops longer than your antenna and no decoupling cap on the PIC.

So, make sure you respect the inductance of 0.5~1nH/mm. For risetimes and V=LdI/dt that means 1nH/mm-ns * dI means the transfer function is 1 volt drop per nanosecond risetiume per mm length times change of current in that rise-time.

Rule of THumb for a trace length to width ratio if @ l/w = 10, L=0.5nH/mm then @ l/w=80, L=1.0 nH/mm

OK if that doesn't make sense, your ground power loops are a big lousy antenna.

Just don't use the breadboard DC rails for anything except LEDs and risetimes > 0.1us and not to power a GSM radio unless a low ESR ceramic cap is added directly across the supply pins.

High speed data only works with twisted pairs of AWG24 hookup wire or magnet wire soldered to a resistor.