The beauty of this design is that it does not have to be tuned to the voice of any particular patient. It can be mass-produced or passed along from one patient to another. In a nursing home, you could have multiple transmitters and one central receiver, which would display the source of the signal, telling the nurse which patient required attention.
Also, the hardware is very simple, and the software could easily be rewritten in whatever language, or for whatever microcontroller the builder is comfortable with.
Nice work, Andrew. It seems feature rich without being too complicated to use. I like the wireless transmission between detector and receiver, and the flashing indicator to alert when mute is on, and the confirmation the patient gets letting him/her know the call is sent. The mute feature could be helpful when the patient has visitors in the room.
I wonder if any readers know of specific fail-safe features that would be required for nursing homes such as mic connections, power supplies, etc.
That is an excellent question. I know nothing about the requirements for medical electronics. I'm certain though, that the gadget could be modified to meet those requirements.
The mute button only prevents the receiver from being activated for 10 minutes, or until it's unmuted. It doesn't have any effect on privacy. The device has been designed so that people talking in the patient's room will not trigger it unless they are close to the microphone and make a continuous sound for 1.5 seconds.
I sent the groan detector system to the lady that I built it for and she is thrilled with it. Her husband especially likes that the transmitter beeps when it's triggered, which tells him that someone will be coming to help him.
This is an interesting device, and a unique application. Possibly the use of the PIC processor made the design easier, but it could also have been done in the analog realm, with a small amount of digital glue logic. That would remove the requirement for programming from the construction, and make the design available for many years, and to a much broader range of people. Yes, a bit more electronic design skill would possibly be needed, but the design would also have been simpler to adjust to changing needs.
Yes, you're right. It probably would not be much more complex to do the gap detection and timing with analog or discreet digital circuits, but this was easier. Also, unless you buy a remote system with a built-in encoder/decoder, you would still need a microcontroller to generate the digital code for it. The simple analog encoding systems I grew up with are not adequate these days. The Chinese company I bought the radio link from has 4-channel remote systems with built-in encoder/decoders. It seems like such a waste for this application, however.
I certainly have the electronic design skill to do it, had I chosen to do so. Changing the software in the PIC is FAR easier than rewiring the hardware if design changes are needed. If the PIC is programmed in a production programmer, it is guaranteed by Microchip to hold its program for 40 years.
Armorris, I guess it comes with "point of view", since I can visualize the circuit fo gap detection as not that complex. And the main focus of this project is a useful device, not as an electronics learning tool. And I was not even thinking about the radio link part of the project when I made those comments.
Now I need to spend some time and figure just exactly how it would be done as an analog-digital mix, but without any processer. Talk is cheap, about 4 cents a pound. Now I need to see if I can provide a similar function in analog.
But your version is still quite an accomplishment, no doubt.
I'm certain that I could have designed the circuit without a microcontroller if I had wanted to, but I felt that this approach would arrive at a working design more quickly and cheaply. Besides, a cheap microcontroller and a little bit of software can replace a lot of discreet electronics. For that reason, almost everything uses a microcontroller nowadays. Even my toaster and my toothbrush have microcontrollers in them. The PIC microcontroller I used in the transmitter unit costs about the same as a 555 timer you might use in a hardware gap detector, but requires no resistors and capacitors. It also performs the 1.5 second timer function and the encoding for the radio link.
If you want to spend the time designing a non-microcontroller version of my gadget, go for it. Once you come up with a circuit, please send me a copy of it. My email address is in the article.
@William K. I like your enthusiasm for lower tech solutions than microcontrollers, philosophically, at least. We could even build a calculator with TTL chips or discreet transistors. Realistically, though, parts count and board space start to lose out on zero parts and space for software. And let's face it, I don't know how to build a transistor so it's all technical beyond primitivism. Now we have devices like PSoC (Programmable System on a Chip) that can combine anything we need -- PWM controllers, video processing, capacitance sensing, multiplexing. And programming is just a matter of using a screen menu with the PSoCCreator.
I understand your DIY drive. From my handle you can guess that I play 78RPM records going back to 1895 but it takes a 5' x 15' closet to house 16,000 songs. It's sad that people don't get the joy I get from that but the iPod won.
What a great innovation by andrew, this might become the basis of saving limitless human lives in the future. I do hope it soon comes out into a product form so that it can actually do some good to us.
And I do hope that the sound acquisition and the filtering system of this device is robust and flexible, because practically every person will have different stroke groan at different frequency, I hope they have catered for this problem in a more generalized & effective way. So that it proves to be marketable.
This device is intentionally designed so that it does not have to be tuned to anyone's voice. The design should be marketable just as it is. If you set the low-pass filter (LPF) to 1000Hz and the gap to 50mS, it would respond to anyone's voice (male or female). I have switches to lower the LPF to 500Hz and the gap to 15mS to get the maximum possible rejection of background noise. The system still does an excellent job of rejecting background noise at 1000Hz and 50mS. Any sound that passes through the LPF and is uninterrupted for 1.5 seconds will trigger it.
I tested it in my house with blaring loud music in the background and, depending on the location of the speakers relative to the microphone, it would respond to my voice only and not the music. I have sinus trouble, which sometimes causes my voice to break up. Feeling that a patient might have the same problem, I added a switch to set the maximum gap width to 50mS. If you didn't want to put any switches in it, I would set the LPF to 1000Hz and the gap width to 50mS. The noise-cancelling microphone helps a lot as well.
There may be another approach to this. A miniature voice recorder, like the Sony IDC-BX700, has a VOR mode (Voice Operated Record). The earphone output can be fed to a small amplifier/speaker which can be located in the caregiver's room. This eliminates the possibility of feedback. The recorder would be placed in the Record mode with VOR, close enough to the patient's mouth. One would adjust the threshold of the VOR and/or distance to the person. Recorders have a microphone input also, so a mic can be easily positioned if the recorder can't be conveniently placed. The battery consumption is low when in VOR mode. Some recorders also have a DC supply input (for a wall wart).
I suppose that would work, but the lady asked for a wireless link and a loud signal that could wake a possibly sleeping caregiver. It also needed to ignore background noise, like her husband's favorite radio program. There are of course, many ways to skin a cat, each with its own set of advantages and disadvantages.
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