Shadow Text Sign With Doppler Radar!

Hello fellow makers,

Today we'll be making a sign that makes a big impact yet is small in scale.

My Pinterest homepage is currently overflowing with companies making use of "shadow signage" where they use a sign mounted horizontally against a wall that then uses either the sun or mounted light above it to cast its shadow onto the wall below.

A big problem I see a lot though is that they don't take into account the distortion caused by projecting the horizontal sign against a vertical wall.

In this Instructable we will solve this problem as well as including a completely hidden doppler radar motion detection circuit to cut down its power consumption.

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To make your own you will need the following:

• Access to a 3D printer Amazon - Creality Resin 3D Printer Halot-Mage 8K
• 6mm O.D. copper pipe Amazon - Copper Tube 15/64inch(6mm) OD 
• 5mm 15deg Ultra bright LED Amazon - 5mm Pre Wired LED

^These come pre-wired with resistors!

• RCWL-0516 Doppler radar module Amazon - RCWL-0516 Motion Detection Sensor
• 18650 Lithium ion battery Amazon - Authentic Samsung25R 3.7V Rechargeable 18650 Battery

^ I highly recommend getting a brand name for safety

• Battery tab set Amazon - Batteries Metal Battery Spring Contact Plates
• 1K ohm Resistor Amazon - 1000 Pcs 25 Values Resistor Kit
• 33R ohm Resistor
• NPN transistor Amazon - 15 Values 750 Pcs PNP NPN Power General Purpose Transistors Assortment Kit
• CA glue Amazon - Bob Smith Industries Maxi Cure/Insta-Set Combo Pack

*As an Amazon Associate I receive a small percentage from sales made through provided links at no cost to you, this helps fund future projects.

If you've ever had to set up a projector you will know all about that pesky keystone correction needed to get a nice rectangular image out of a trapezoidal one.

Whenever your projection surface isn't 100% perpendicular to your projection it causes the image to be trapezoidal as demonstrated by the rendering below. You can see that our projection image is rectangular but not the projected image.

To solve this problem we need to invert the projection, make the projection image trapezoidal so that the projected image is rectangular as rendered below.

The way I do this is to start with Adobe Illustrator and create the text I want in my chosen font, then under the Effect tab choose Warp and then Arc. This will open up the Arc options window, first you want to set the Bend to 0%, next you will set your vertical distortion this is what will warp your text into a trapezoid.

For me setting the vertical distortion to 15% worked well and gave a good rectangular projection, you can use the render function in Fusion 360 to test out the amount needed as I did with the above images.

Once you are done you can export the text as an SVG file and use it to create the projection plate in the next step.



Some of the Fusion 360 veterans might know this but this was the first time I used this feature and it was so helpful with the design of this project.

When you change the appearance of a model in Fusion 360 (Modify>Appearance or by simply pressing "A") under Miscellaneous>Emissive or by simply searching for LED there are multiple light sources that you can add to a face of an object that emit light when rendering an image.

To simulate a directional/spotlight like the 15deg 5mm I'm using in this project I simply cut out a sphere into a cylinder and applied the "LED 50lm" to the face of the sphere, the focal length can be adjusted by modifying the depth of the sphere.

Now we will use Fusion 360 to design the wall mount that will enclose the electronics and hold the projection plate and light.

To make the shadow sign as clean and minimalist looking as possible I didn't want any wires going to the wall mount so we will have to use a battery, that solves one problem bust unfortunately presents another. We don't want to be constantly charging the battery so we need to make the whole circuit as efficient as possible, that's where the microwave doppler radar sensor comes in.

I chose to use the RCWL-0516 module because unlike the more conventional IR motion sensors this unit consumes a maximum of 3ma of power and it can be fully enclosed in a plastic enclosure and doesn't need the pesky exposed Fresnel lens like the IR modules.

The design of the wall mount was largely dictated by the 18650 battery that I will be using for the power size, the mount consists of an open battery holder for easy swapping, a enclosed compartment for the electronics and a slot for the LED assembly and text projection plate.

All of the parts were printed on my Creality Halot One using ABS-like resin but can also be printed on an FDM printer.

To cast the shadow we will be using a 15 degree ultra bright white 5mm LED suspended above the shadow plate with a 6mm copper pipe.

I chose to go with copper piping to hold the LED in place because after assembly you will need to make some fine adjustments to get the light focused in the right spot and copper allows us to easily bend it into place, plus I think the copper just gives it a great steampunk look.

You will need a copper pipe around 20-25cm long (the one pictured was 30cm but I ended up cutting it shorter) with a 6mm O.D. with 5mm I.D., this gives a nice flush mounted LED on the end. You want to bend this piece into a candy cane shape.

For the LED I recommend getting something like the Nichia GS or like I'm using the Cree C503D, these have some crazy brightness for simple through hole 5mm LED's.

Next we need to solder some wires onto our LED to extend the leads into the enclosure.

The wire needs to go from the LED, through the pipe and then through the wall mount into the electronics compartment so I recommend about 40cm of thin wire for each lead. I covered the solder joints with heat-shrink tubing to prevent shorts to each other and the copper pipe.

With the leads insulated you can now feed the wires through the copper pipe and adhere the 5mm LED to the end of the pipe using some CA/super glue.

That's the light source finished

Now onto the electronics.

The output pin of the doppler radar module should be adequate to drive a single 5mm but as normal NPN transistors cost next to nothing I always prefer to add an external transistor to drive loads and this also allows us to add a stronger light source if we wanted to.

I used a BD139 NPN transistor which is a bit overkill but I have a lot of them on hand, I recommend you simply use a commonly available 2N2222.

You will start by soldering the emitter (leg 1 on 2N2222) to the GND on the RCWL-0516 module, then the 1K ohm resistor goes from the OUT pad to the base (leg 2) of the transistor and finally the 33R ohm resistor gets soldered onto the collector (leg 3) of the transistor, the other end of the resistor will get soldered to the negative/GND lead of the LED later and is there to limit the current to the LED.

Next solder on a positive (red) and negative (black) wire to the VIN and GND of the RCWL-0516, these wires will need to be ~0.8mm thick to fit. After soldering they can be fed through the slots on either side of the battery cavity as shown bellow and soldered onto battery tabs, the positive goes to the flat tab and the negative goes to the tab with spring attached.

I used CA glue to adhere the tabs into the indents of the holder.

Our power source is ready and we can now install the LED.

On the side of the hole where the copper pipe goes into the wall mount is a hole that goes to the electronic enclosure, we need to feed the LED's wires through this hole before pressing the copper pipe into place.

The positive (anode) wire of the LED gets soldered directly to the VIN pad on the RCWL-0516 module and then the negative (cathode) wire goes to the 33R resistor on 2N2222 transistor.

You can insert the battery into the mount to make sure the LED lights up, by default the RCWL-0516 stays on for 2 seconds intervals but continuous if there is movement.

With everything working you can place the sensor into the mount (I used some double sided mounting tape on the back of the module to hold it securely) making sure the side with the IC and wavy trace is facing forward.

Now go ahead and attach the lid of the enclosure.

With our shadow sign ready and working it's time to add some finishing touches.

As you might have seen in some of my previous Instructables since I've found these chrome markers I love to make the faces of the embossed text chrome, I think it adds a real premium look to printed parts.

I decided to go with normal 15mm double sided mounting tape instead of something more permanent as the whole assembly is very light with most of the weight coming from the battery, this way you can move the sign around by just spritzing a bit of alcohol (I usually just use 70% alc hand sanitiser) on the tape.

I hope you guys find this Instructable useful and if you have any questions please feel free to leave me a message or comment bellow.

Thank you for taking the time to read through my project and as always..

Happy making!