Introduction: Flashing LED Tell-Tale Heart

Recently my American Literature class read The Tell-Tale Heart. When I was preparing for the lesson, which was going to be a Reader's Theater type activity, I really wanted to have a pulsating heart. The beating heart that the main character thinks he hears is an important part of the story and I wanted my students to really understand the effect the beating heart had on the character. Using something auditory wasn't going to work for us, so I came up with a way to make the beating heart visual. By using a fast blinking LEDs I could make adjustments and show students how the heart sounded to the main character at different points in the story.


Felt sheets

Heart pattern (printed from the internet)

Fast Blinking LEDs

Slow Blinking LEDs

Resistor (200ohm comes with the LEDs)

Conductive thread

Embroidery thread, needles

Coin cell batteries

Snap closures


Step 1: Patterns

The first thing I did was to find a decent clipart anatomical heart and print it. I cut out the heart and traced it on my felt and then ended up cutting the heart in sections so that some parts of the heart will be red and some blue.

Step 2: Sew

I used black embroidery thread to sew the heart section together. I went with a simple stitch and didn't try to hide the stitches because I wanted that damaged just-sewn-back-together heart look. For the back of the heart, because that's where I'll put my battery holders, I decided to go with a solid color.

I also ended up using purple thread and stitching veins into the heart.

Step 3: LED Circuit

I used the fast blinking LED because the slow rotating one wasn't rotating fast enough.

I bent the legs of LED and the resistor and used conductive thread to secure both of them, (two separate strands of thread and two separate needles, one strand for the positive leg and one strand for the negative leg).

I also glued a small piece of felt between the negative and positive threads to prevent them from touching (pic 4).

Step 4: Battery Holder

For the battery holder, I followed the instructions from this blog. You're basically using sew-on snaps to create an on-off button.

Using the positive thread and needle from the LED, attach one side of a snap to the back of the heart. Sew on well and then tie off and cut. Repeat with the negative side. Make sure the positive and negative threads do not cross.

Trace the battery onto a piece of felt and add two small tabs on each side (do this twice, you need two pieces to make a pouch). Cut out and then sew on the opposite side of the snap with regular or conductive thread. Then using the conductive thread sew from the snap out towards the center of the circle and make a few stitches. Tie off and cut.

Repeat this for the second snap. Sew the other button also with conductive thread and then place the other piece of felt on top, and sew several stitches. Then sew towards the middle as you did with the first piece.

Finally, test the snaps and the circuit to make sure the LED lights up. If it does, go ahead and sew 3/4 around the battery holder---leave an opening for sliding the battery in and out.

Step 5: Final Touches!

Before sewing the sides of the heart together, I tested my circuit a few more times. Using embroidery thread, I stitched along the outside of the heart, about 1/2 through I started adding batting to fluff the heart up--careful not to put too much around the LED so it wouldn't stifle the light. Keep sewing and add more batting until the heart is completely enclosed.

Step 6: Done!

Depending on how I hold the heart (or how hard I press on the battery) the LED goes back and forth between slow and fast, light and bright. It's really cool and my students have really enjoyed it.

I think next time around I'll have my students make their own heart.

Heart Contest

Participated in the
Heart Contest