Monitoring Wi-Fi Signal

Hello, I'm curious if the following concept is possible, and what hardware I'd need to get started. I'm new to the arduino and programming, and hoping this current need would give me the reason to learn!

The problem: I have a cellular Hotspot that I use in a remote cabin for internet. The Hotspot broadcasts Wi-Fi which is used to connect devices so I can control remotely. However, the Hotspot has a history of locking up or shutting down unexpectedly. I'm left unable to reach the connected devices and can't restart the Hotspot since I'm hours away.

The idea: Use an arduino to monitor the presence of the specific wifi network the Hotspot broadcasts. If this signal is lost, trigger a servo motor to rotate a specific angle that will depress the power button on the wifi and cause it to turn on/off. I'll have to figure out the specific sequence of the servo motor to push/hold/release and appropriate timing to make it work right as well as the loop to retry a specific number of times.

Questions:

  1. Is this reasonably possible for a beginner?
  2. Is the Uno the right choice for this?
  3. Are there other boards / drivers / motors that care commonly used for simple tasks like this?

Thank you for reading this! I appreciate any thoughts or help anyone is willing to offer.

Yes, but I can think of other ways to do it.

First, I use Wemos D1 Minis anywhere that I need WiFi.
One of those is a net monitor that pings 3 of my my local servers plus one external IP at random (Google, Amazon, etc. I ping them at random so to not look like a DDOS attack). If any ping fails, I get a red LED. This way I can tell at a glance if one of my servers is down or even the router.

You could do something similar, but instead of a rube-goldberg servo arrangement, why not just interrupt the power to the hotspot with a relay or MOSFET?

More specifically, what does "depress the power button on the wifi" mean?

Hi mtdave, like Steve I've built a network monitor/logger and you can find full info on my site here

I'd agree with Steve there has to be a better way to cycle the power.

However, the Hotspot has a history of locking up or shutting down unexpectedly.

How is the "hotspot" powered? What happens if/when the power fails?

Thank you for the replies and thoughts. The Hotspot is powered by a UPS/ Battery Backup as will the arduino be powered if it is feasible. The Hotspot must be turned on/off with the power button. Removing / connecting the power to the device does not force it to turn on. The power button must be held down for 2 seconds to power it on. This is the reason I'm proposing using a servo motor to simply actuate the button. I have not disassembled the Hotspot to see if the switch could be replaced with a leads to connect to the arduino directly, but I'd prefer not to modify the unit for now.

Hoping this is possible!

Have you checked whether the Hotspot has a programmable option to turn on when powered up?

Can you open up the Hotspot to access the pushbutton wiring, and trigger it with an optocoupler or relay?

Unless you have reasonably good mechanical construction skills, you are in for a struggle with the servo/pushbutton approach. Hobby servos burn out if stalled for any significant length of time. A solenoid plunger would be easier and more reliable.

mtdave:
Thank you for the replies and thoughts. The Hotspot is powered by a UPS/ Battery Backup as will the arduino be powered if it is feasible. The Hotspot must be turned on/off with the power button. Removing / connecting the power to the device does not force it to turn on. The power button must be held down for 2 seconds to power it on. This is the reason I'm proposing using a servo motor to simply actuate the button. I have not disassembled the Hotspot to see if the switch could be replaced with a leads to connect to the arduino directly, but I'd prefer not to modify the unit for now.

Hoping this is possible!

What is the model of this mystery hotspot? Is the UPS built into the unit or does it plug into the UPS? Is it leased or can you make a minor modification inside?

Hi Steve, the Hotspot is a Novatel Jetpack 8800L thru Verizon. It's owned outright, so modifications are not a problem although I do use it outside of the cabin sometimes. I've not been able to disassemble the unit yet to see if the power switch could be replaced / supplemented with a wired connection but as soon as I can get a small torx screwdriver I'll have a look.

Originally I had considered using a solenoid to push the button but thought a servo might be easier. Mechanical construction is absolutely no problem, just not at all knowledgeable how to read the presence of a wifi signal and trigger a solenoid if the signal is dropped for "x" seconds.

The UPS is a stand alone unit that powers the Hotspot and other items.

Really appreciate the help and recommendations on hardware to detect wifi and process /trigger the relay or stepper.

Thank you!

mtdave:
The UPS is a stand alone unit that powers the Hotspot and other items.

Then, just disconnect the power from the UPS to the HotSpot with a relay.

Hi,
@SteveMann I think this is the reason power down/power up will not work.

The power button must be held down for 2 seconds to power it on.

It sounds like a momentary power button, not a toggle type.
So apart from holding it down for 2 seconds, it is open circuit all the time.

Tom... :slight_smile:

If you have just basic mechanical skills, you can easily create a mechanism to depress a button and have it hold for whatever time you like.

if you try to create torque and stall the servo, you will have problems.

if you take a cam on the servo and make it so that the maximum point on the cam, presses the button properly.
then you only need to rotate the cam until it is in position.

if you have a solid model machine, or an old erector set, it is simple to create such a button press device.

pro's & cons.

Mechanical approach - moving parts, needs a solid mechanical fixing to the device. Higher current demand while moving than an electrical solution, but no current when stationary. Perhaps more fail-safe in that the actuator will not move if the supply is interrupted.

Electrical approach - adding a relay to the device involves opening it up, and managing a controlling signal to provide the right stimulus. Perhaps the relay (or FET, whatever) can be powered from the device's supply.

johnerrington:
Mechanical approach - moving parts, needs a solid mechanical fixing to the device. Higher current demand while moving than an electrical solution, but no current when stationary. Perhaps more fail-safe in that the actuator will not move if the supply is interrupted.

Not fail-safe if you use a cam and it sticks in the actuated condition with the hotspot disabled. :astonished:

johnerrington:
Electrical approach - adding a relay to the device involves opening it up, and managing a controlling signal to provide the right stimulus. Perhaps the relay (or FET, whatever) can be powered from the device's supply.

If the button on the device is connected to its local ground, which is quite likely, then you have many options. A relay would neither be necessary or convenient as supplying it from the device means that the coil is connected into that device and there is no meaningful isolation anyway.

You want to use an opto-isolator for complete isolation of the ESP8266 (because you said WiFI) from the hotspot circuit, but you may need a switching transistor if you need more than a few mA to trip the button circuit (and you most likely do not need anything like that current anyway). It is most likely that an opto-isolator will perform the complete interface, needing only a current-limiting resistor for the input LED side.

pros and cons
pro : Mechanical device does not alter the device
mechanical device can be done easily and removed instantly.
con : repetitive button press can cause wear, degradation or failure.

pro : electronical device does not wear out
con : not easy for a noob to implement.
it really comes down to what you are more comfortable doing.