Intro: Head Mounted Laser Pointer Communicator
Why? For someone paralysed apart from some head movement who cannot otherwise communicate.
As you may see I have made a few devices as aids for disabled people (RFID music box, Kindle page turner, giant nurse-call button). Colleagues know I do this now, so I get approached sometimes to help people out. A small amount of tech can sometimes transform someone's life.
This one was made for someone in hospital with an illness that has at present robbed them of all movement apart from some head movement. They cannot speak as on a ventilator via tracheostomy. Very frustrating for someone to not be able to communicate even basic thoughts.
I had been trying some free software from around the world that tracks head movements using a webcam in a laptop, to select letters on the screen, with some success (The "HeadMouse" face-tracker in conjunction with Click-n-Type on screen keyboard, also Can-Assist "Dynamic Keyboard", also tried the "Eyewriter" from Instructables, for those who might be interested).
However, these laptop based higher tech solutions do mean that ultimately others would have to set up the laptop and open the relevant software(s) to make this work. On a busy day this may well not happen.
Therefore, it occurred to me that there is a low cost solution that essentially does the same thing, i.e. a head mounted laser pointer plus a board with letters and key words on it. The KISS (Keep It Simple - Stupid!) principle in action.
There are a number of YouTube videos of people exercising their cats by attaching a laser pointer to their heads, however here is a more serious use.
1) A cheap head torch. Get one that takes regular batteries i.e. not rechargeable. Typically they use 3 x AAA batteries. If the front tips up and down that is a bonus for positioning of the laser in most comfortable place for the user. Mine had battery box at the back of the headband which would be annoying if lying in bed, so need to move it to one side or get a newer variant which has the batteries behind the LED light at the front.
2) A laser module. Get one that runs at around 3 Volts.
3) Optionally a regular LED. This reminds staff the laser is on so they do not forget to turn it off after use. It is not going to work with a flat battery so make this "power-on-reminder" LED bright!
4) Resistor to go with this LED.
5) Something to house the Laser. I 3D printed mine but something like Sugru or mouldable plastic would be just fine.
Tools: Soldering iron. I use 3x magnifying glasses from hardware store to do fine work. I am unusual perhaps in not using "helping hands" alligator clips to hold my items while soldering them, I prefer a big blob of Blu-Tack.
Commercial versions of this idea do exist. For example there is one that clips to a spectacles frame. This one was put together in order to see if the person was able to use it and found it useful.
Step 1: View of Device in Use
Here is a view of the laser being used (not on my head here) with a commercially available letter board.
Step 2: Head Lamp Before Modification
Here you see how the front bit with the LED's in can tilt downwards. This will be used to get the laser at correct angle for the user. If they are stuck in bed it is convenient to be able to aim the laser down a bit.
Step 3: Unscrew Back of LED Housing
Designs of these lamps differ.
Basically we are going to use 2 of the 3 battery slots in the battery box (which typically hold 3 x AAA batteries) and we are going to replace the LED's in the lamp with our Laser module plus the "power on reminder" single LED.
Here I am unscrewing back of the LED housing.
Step 4: Pull Out the Internals of the LED Housing
Here I am pulling out the internals.
I have removed the 6 LED ring from the housing.
In my case the on/off switch was also in this removed part, so we want to keep that.
I have exposed the red and black wires that went to the ring of LED's as I am going to connect them to my Laser and to my single "power on" indicator LED.
Step 5: Ring of LED's Removed
Here is the ring of LED's removed.
Not planning to use this part again.
Step 6: Modify Battery Box to Take 2 Instead of 3 Batteries
I am going to by pass one of the batteries in the battery box so it only takes TWO AAA batteries instead of three. This will then give around 3V for the laser.
I solder a wire to the bottom left connector (file it to make shiny, then put blob of solder on it, then add the wire).
Step 7: Solder Wire to Top Left Connection
Other end of wire is soldered to top left battery connection.
NOTE: There is a black wire soldered to back of this spring mounting, if you overheat it, it will fall off unseen and break the circuit. Keep the soldering down to quick bursts with time to cool down in between.
So, having done this, you can see I have bypassed the left hand battery, so we can just put the middle and right hand batteries into this battery box giving 3V to the Laser.
Step 8: Pick a "power on Reminder" LED
Pick a bright LED.
Take note of the current in milliamps, the "forward voltage" and the supply voltage (in our case just over 3V).
Step 9: Decide Which Resistor to Use With This LED
We want to limit the current to our power on reminder LED so it does not burn out.
If you search online for "LED resistor calculator" there are a few that come up like this example.
Enter the supply voltage, the forward voltage and current rating of your selected LED and it will tell you what value of resistor to use with the LED. Here is it 18 Ohms.
Step 10: Select Your Resistor
Here are the 18 Ohm resistors from my big resistor stash.
Step 11: Neatly Solder It to Your LED
Solder it to your LED and keep things compact. The -ve wire will go to the leg of the LED next to the FLAT edge. The +ve supply will go to the leg next to the curved edge. The resistor here is being soldered to the +ve leg.
Using Blu-Tack to hold it all still.
Step 12: Make a Mounting That Holds the Laser and the LED
It depends on the shape of the hole remaining after you have removed the LED's from your headlamp.
In my case the hole was a simple circular tube. I 3D printed the red thing to hold both the Laser and also the "power on reminder" LED. You could use something like Sugru instead.
Here I have soldered up the Laser to the black -ve (ground) and red 3V +ve wires that previously used to go to the ring of LED's on the front of the headlamp.
Step 13: Rear View of the Laser and LED Housing
Another view of the plastic insert I made to hold the Laser and "power on" LED.
Step 14: Glue the Laser and LED Into the Front of the Head Torch Structure
I used a glue gun to fix the Laser into my red housing and also the LED.
The red wire sticking out of the housing (now 3V +ve) was soldered to the +ve leg (via the resistor) of the LED, and also to the +ve terminal of the Laser.
The black -ve wire sticking out of the housing was soldered to the -ve leg of the LED (the one beside the flat side of the LED case) and also to the -ve terminal of the Laser.
Step 15: Replace the Rear Insert We Removed Earlier
Replace the rear insert we removed at the start, this has the on/off switch in it which we need to keep in a working state. Here I am replacing the tiny screws that hold the rear insert in place.
Step 16: Make a Cover to Stop People Trying to Put in the Third Battery
I glued a cardboard tube into the battery slot where I had previously bypassed the battery connections, to stop people trying to force a third battery into this location!
(If it can be broken, then it WILL get broken). Try to design human error out of the system as far as you can if you are going to let others loose with your creation.
Step 17: Start Using It
Here is how you use it. Obviously someone has to be near you to write down what you are trying to say by pointing at the letters and key words.
An alternative is a small "white board" wedged into the foot of the hospital bed with the letter board hand written onto it using a marker pen. The laser will work OK over the length of a bed. The smaller the maximum range of head movement of the user, the further away the letter board needs to be to amplify any movements. A little trial and error will be required to optimise it for each user. Don't forget to adjust the Laser angle down a little if it helps keep the user in a comfortable position.
Step 18: Example of Currently Available Head Lamp
I am not sure if the head lamp I used is still made.
However here is an example from ebay of a similar one. It is just a few dollars.
The main thing is it takes regular batteries, usually 3 x AAA batteries as shown here. Do not buy one with rechargeable batteries as then cannot easily modify it to reduce the voltage to 3V for the Laser. Some have battery box on the front behind the lamp and some have it on the back of the headband as in the one I used for my project.