Are there plug-in wireless TX/RX modules I can buy and just plug into the Arduino and the PC USB ports to replace the cable (no complicated programming, resetting, etc.) so I can download to the Arduino and use the serial monitor and do everything the same as the serial cable over longer distances. I have read various methods but they all seem very complicated and you have to reset the Arduino after a download.
My Arduino in in my cold garage and I want to connect to it from my comfortable armchair by the fire in my study.
Not with the serial monitor. You can do it using a proper terminal programme, which you probably should have been using all along, and can be had for free. I use RealTerm.
You can then use bluetooth, best described by some guru around here as serial without wires.
You can do this using exactly the same programme as you are using now.
Since the environment may be a bit taxing, I think you would be best off using BLE - Bluetooth low energy.
Your problem starts at the study end.
I have never seen a PC with bluetooth installed. This is not necessarily a bad thing, but I am not aware of any BLE device for desktops - mainly because I have never looked for one. I have never succeeded in using my USB bluetooth in my desktop and I can't comment further on desktops
While most any laptop comes with bluetooth, I am not aware of any with BLE - for the same reason.
BLE is pretty common on phones these days and they are likely to be a better proposition than using a computer anyway. If you don't have the means for bluetooth reception in the study at the moment, I submit a cheap Android phone would be the best option - particularly if you can get one with BT4. I use a cheapo Huawei and Bluetooth Graphics Terminal
You may be able to risk $3.50 and try a plain-vanilla HC-05 to prove the point. They have a nominal range of 10m, and will go through an internal wall easily enough. You may find it works fine.
You might find the following background notes useful
Thanks Nick, I have used the HC-05 as a serial connection. That is (reasonably) easy. What I want is to replace the USB cable with wireless and do everything like I had the cable plugged in. You don't need to load a special sketch into the Arduino in order to use the serial cable, you just plug in and use the IDE. That is what I want. Do exactly what the dumb cable does. Just replace the 5v/0v logic levels on the cable with high/low wireless signals and vice-versa decode back to 5v/0v levels at the other end both ways like a wire. No special programming needed. Doesn't sound too difficult - just radio hardware and a good hardware designer. No one asks which end of a wire is the master and which end is the slave.
There are also cables for usb that are 10 or 15 meters, two or three of them can be connected together. I think they have electronics on both ends of the cable. I have one of 10 meters and I add a normal usb cable of 5 meters to get 15 meters "range". The Arduino might need a power supply to power the Arduino.
I could add a powered usb hub and add another cable of 5 meters.
Bluetooth is most often used for wireless upload of a sketch.
Can the Arduino Yun upload a sketch to the ATmega32U4 ? The Dragino "Yun" compatible shield can do that.
You'll need to figure out how to supply +5V to the USB port on the Arduino side. The slave (non-host) end of a USB cable is designed to NOT drive +5V out the USB port (because the host always does).
The only downside is they don't pass on the reset/wakeup feature/function of the USB protocol. That means I can't use them to talk to my AzteegX3pro printer controller because the Arduino IDE and Repetier host both require this feature.
If all you want is a low speed (under 1M) Bluetooth serial link using USB connectors then they should work for you.
Buy two of them, set one up as the master and one as the slave and then set them up so that they automatically pair only to each other.
Here's a link to one of the best descriptions of the steps needed to configure the two modules. connecting two USB modules