Ben Heck's Smart Switching Headphones

Ben takes apart a baby monitor to see if he can build the circuitry inside of it. Inside the baby monitor is a radio module, a glop top integrated circuit that runs everything, power regulator, crystal that runs the circuitry, some caps, an antenna, and an IC that might be some sort of memory or identification chip. It might be possible to use the battery that powers the baby monitor to also power the switching circuit.

The speaker could also be removed entirely and turned into a headphone jack. In order to see if the amplification going to the speaker needs to be knocked down a bit to prevent hearing damage, Ben hooks it up to a battery to see how much current it draws. It’s drawing about 50 milliamps which isn’t too bad so Ben continues testing with Felix simulating baby sounds.

For this project Ben uses the ADG 436 integrated circuit, a two channel switching circuit, so they can use logic on or off to switch from one channel to another. The outputs are hooked up to headphones and a pair of Nintendo Game Boys that act as inputs. There are pull down resistors so that both of the inputs are set to low.

Ben looks for a way to combine the switching circuit with the baby monitor. The switching circuit has been tested to work down to about 1.8 volts. He then probes around to see where all the voltages are so that he can power the switching circuit. He finds a boost regulator used to boost the lower level of the batteries up to a stable level of 3.2 volts for device operation. He also finds that the system voltage can be found on many test pads around the unit as well as the positive terminals of several of the electrolytic capacitors. He then uses his bench power supply to simulate the batteries losing charge and discovers that the system kept working down to around 2.3 volt battery level.

Once Ben is able to get the baby monitor to switch correctly between the inputs he goes to work getting it to switch automatically. By default the switching circuit plays the music input channel. Ben uses a 555 integrated circuit timer and some capacitors to get it to switch over when noise is detected on the other end and leave it switched for a minimum amount of time. Attaching some small surface-mount capacitors around it will allow the 555 to be triggered by the LED indicator and then it will keep the signal line high for four seconds so that it can switch back to music if an insignificant sound is detected.

Ben wires up a 555 timer in monstable mode, aka one shot mode. When the indicator LEDs are turned on what’s actually happening is that they’re being sourced with 2.6 volts and then the microcontroller pulls the other side of them low allowing current to flow through the resistor. Normally the LED is high but when it’s active it’s low. The LED is hooked up to the input or the trigger of the 555 so whenever there is a falling edge on the 555 the one-shot triggers for a specific amount of time. This amount of time is controlled by a specific resistor and a capacitor.

[ChrisBurnes]

I see a lot of criticism about the "hacky" nature of your mod. I like it, it is more accessible and realistic for what other makers have access to. No custom printed PCB's, no 3D printer parts, no CNC laser cut stuff. Keep it up!

I like the "Hey, there is a problem, lets solve it with electrical engineering" attitude, over-engineering not required.

Also, I just modified my baby monitor last month to charge via USB! now my wife can charge it with a USB battery pack if she doesn't want it to be tied to the wall.

[hoppend]

Cool to see my suggested idea come to reallity.

[adamsfusion]

An item that doesn't affect me at all, but I'm always still so entranced with the build. Thanks Ben (and crew)!

[niqhtt]

This is really good. A very practical project.

And you missed a big opportunity at the end bit for "If you build it, they will come"

[FalcoTheImpaler]

"I'm making a lot of noise now, I'm making so much noise, this is a LOT of noises I'm making... All this noise is a lot. Sure is a lot of this noise"

[guycrew]

Hey Ben! Do you think you could build a video switchbox that would switch inputs when one was active?

For example, if I have a bunch of consoles plugged into the switchbox, I could just turn on the TV and turn on the console I wanted and the switchbox would switch inputs to the console I just turned on. Also, if there are two on at once you could switch to the one most recently turned on and then cycle through the available inputs with one button. Maybe have LED indicators for active inputs? By the way, in my situation I would make the device for composite video, but, of course, you do what you want.

I would find this useful because I collect video games and consoles and running a bunch of composite inputs into one TV is a bit of a pain, nevermind switching between multiple switchboxes because one doesn't have enough inputs. Though this may not solve my particular problem, it would remove one step of the process and would help people forget about the mess of wires going on behind their TV.

Also, if this project is too easy, see if you can make it modular so you can add more input options for future expansion.

[jazzbolden]

Ben I really enjoy your channel. I absolutely have no clue about electronics, but I enjoy watching your shows and I'm amazed by the ideas that you, your crew and your audience come up with. keep up the great work.

[azyfloof]

I lost my shit at "Bruce Willis is really dead" 😂😂😂
Loved Felix "baby noises", too! Very VERY funny!
Great build, Ben!

[wnzrz]

Next project: auto record when Ben Heck says something silly because it's awesome

[GoGreenMan]

Do you happen to have some sort of wiring diagram for this? even a theoretical version. I really like the idea of how this circuit works and would like to use it in other applications. thanks

[justinrowan]

Great minds think alike! I have this same monitor for my daughter, and planned out to do nearly exactly what you've done, except I would use the red LED to trigger a separate microcontroller which would do some logic (X number of loud bursts in Y seconds) so that a cough or short bout of crying doesn't wake us up.

[pesterenan]

Man, "sounding" projects are so much fun to watch being made. You guys going crazy screaming to the baby monitor made me laugh a lot xD

[talontsi]

Someone donate a new set of screwdrivers to this guy... that one looks abysmal.

:)

Keep up the good work Ben!

[sprybug]

Ah, now this is more down my alley. I use as much existing stuff as I can on my projects because I'm poor. lol. So, no way to make my own cases from scratch. It reminds me more of the portable projects I work on. Right now I'm working on my second portable NES, but this is one is completely hand held and uses the case of some kid's touch screen organizer that was big enough for the job. Flatscreen portable 7 inch LCD, an original and modified NES, along with my own added circuitry and there you go.

[sousamaster]

Can you post the first rendition of the "push button audio line switch" schematics we see after the 4:08 mark? I would really love to build that part for myself!

[Klingon]

How would you add the ability to pause the music on an iPhone while it was switched over to the baby monitor?

[dascodraws]

is there a channel you guys would recommend for a beginner in electronics?

[rohithks]

I want to make a circuit to automatically switch from primary audio input to secondary audio input when there is no input from primary input. Can you please help me??

[ZacharyBittner]

I'm curious if you could hack those cheap handheld Chinese consoles from websites like deal extreme into something more usable.

[donvittoriophoto]

I'm liking the beard. I hope you grow it out, it suits you.