Category: assembling

Making of an ESP8266 Vibrator Development Board – traps and pitfalls

About a year ago I made a ESP8266 based design for a vibrator development board including IMU, motor driver and battery charging. The design was based on the Adafruit ESP Huzaah, but I used components of Seeedstudio Open Parts Library. This is a library of parts (IC, connector, resistors) which are stocked at Seeedstudio especially for their PCBA (printed circuit board assembly) service. PCBA is really great. Instead of tinkering and soldering on your own you can send the design to Seeedstudio, they make the printed circuit board and assemble all parts. Unfortunately the main part – the ESP8266 microcontroller – was missing in the Open Part Library . So I turned to use the affordable ready-made WeMos ESP8266 boards (see here).

In June 2017 I took a closer look at the PCBA service. At that time the OPL offered two variants of the ESP8266. But even better: You could order almost any part. The difference between using OPL parts and other parts was the time for the assembly as it takes more time to order parts which are not on stock.

So I ordered two boards. The boards are round with a diameter of 5 cm (that’s the size of a wireless charging coil). As I had a coupon the two boards were only about 50US$. Including delivery! And even better: Seeedstudio delivers from a logistic company in Germany. So I had not to pay any taxes. Great. But… unfortunately … I made beginner’s mistakes…during design.

  1. Problem: As the board should be programmable by USB connection you need a USB to serial bridge eg. one of the FTDI ICs. This bridge has two important connections TX (transfer) and RX (receive). And the ESP8266 has the same TX and RX. But don’t connect them. Instead you have to connect RX to TX and vice versa. (Well I should have know, when I soldered null modems maybe 20 years ago or more…)

    Taken from Sparkfun

  2. Problem: When using the serial monitor of the Arduino IDE you need another connection: RTS (ready to send). Unfortunately the used serial bridge – the FTDI FX230XS IC – had no RTS. (There is a circuit which works without RTS, but I didn’t know.)
  3. Problem: I used GPIO0 for driving the motor, that’s why auto reset doesn’t work. So I had to short-cut GPIO0 and GROUND for uploading a script.

So I tried to fix the problem. At first I had to cut the wrong connections. On the bottom side of the board the RX and TX wires are quit good accessible. So I could cut them using a dremel.

In the next step I had to connect the RX and TX headers of the FTDI chip with the ESP 8266…

The green clamps were used to shortcut another wrong connection.

Finally upload with the Arduino IDE was possible, but no debugging using the serial monitor. Battery charging seemed to work, too, although this needs more time for testing. WiFi worked. Essentially I could upload a script which made one LED blinking. And I could start the WiFi manager.

Debugging such a complex thing like a ESP8266 without serial connection is almost impossible. But then I found RealTerm. This is the only terminal program for Windows where you have all options to use or not use serial sync mechanisms like DTR, RTS etc. It is made to make a serial connection work even if you have only TX, RX and GROUND.

Here you can decide to ignore RTS and/or DTR by pressing “Clear”. (Read more about this here.)


And finally it worked. The ESP8266 sends debug text to the serial monitor. The transmission maybe scrambled, but it is still readable. Realterm – a really great tool for debugging serial connections.

Readings of the MPU9250 (accelerometer, gyro)

Probably it is more reasonable to use a bread board for the development of a design. But customizing an open source design on the PC and then get it assembled for a reasonable price – for me it’s like a dream come true. But as you see – all your efforts can be worthless.

But I will do it again…



Basic Node for the Internet of Sex Toys – part 2: 3d printed form, assembly, molding

In this series of posts we describe how-to make a vibrating sex toy which is part of the Internet of Things.

part 1: Basic Node for the Internet of Sex Toys

part 2: Molding the Basic Node

part 3: Software for the Basic Node

In part 2 we describe how-to make a mold form for the basic node. We need three forms:

  • the mold form which consists of two parts
  • the inlay which protects the electronics of the basic node
  • a “hanging” for the inlay




We used Tinkercad to construct the parts. The molding form is based on Tinkercad’s banana form. You can edit and share them from your browser:





Print out all forms. The STL files are available at Thingiverse. You might want to use XTC or similar for smoothing the inner part of the mold form.

Assembling the Inlay

We use the inlay to protect the electronics.

Simply put the electronics inside so that the upper body of the switch is on the same level as the upper inlay. We use hot glue to fix the basic node.

Then fix the receiver coil of the wireless charging module on top of the inlay. The next step is to fix the hanging at the inlay.

Now fix the LiPo battery on the bottom side of the inlay using hot glue or similar. Fix the wires. Finally you might fix the wires of the vibration motor next to the middle of the LiPo battery.

Use tinkering wire to fix both parts of the molding form.

Put the inlay in the form. Fix the hanging with a tape or similar. The motors shouldn’t touch the inner part of the form.

Now prepare the silicone. We use Shore A 45 silicone (approx. 250 ml) from It is hard but still a bit flexible. You may add color, too. You have about 10 minutes to stir the silicone and poor it in the form.

After some hours you can remove the form. As you can see there is overhang which make removing the form very hard. The form could break when removing. Better preparation of the form (eg rasping) could improve the results.

If the blue LED of the Wemos board is still active you were successful.

Now you need a charging station. The construction is shown here. It is also possible to connect the sender (or transmitter) module with a 5V power source (eg. from the USB port). Just put the bottom of the molded basic node on the sender coil.


In the next part we introduce an updated version of the software including over the air update and WiFi management.

Basic Node for the Internet of Sex Toys (part 1)

Wemos mini modules: ESP8266, motor driver and battery charging (in the middle); Wireless charging module (right side); wireless charging coil (top side); encapsulated vibration motors (left side)

In previous posts we showed how to build a vibrating sex toy in principle as part of the Internet of Things (IOT). In addition we have selected a hardware platform – the popular ESP8266 – for controlling a vibrator motor, gathering motion data and connecting to the internet. Now we want to build the toy itself.

part 1: Basic Node for the Internet of Sex Toys

part 2: Molding the Basic Node

part 3: Software for the Basic Node

Brief Review of development boards

There are a lot of development boards which are equipped with the ESP8266. The popular NodeMCU was already introduced here. Here is a quick overview and comparison:


  • plus: very popular, cheap, USB connector for programming
  • minus: quite large (for being part of a sex toy), no support for battery charging

Adafruit Feather Huzaah ESP

  • plus: USB connector for programming and battery charging, smart form factor (only 23 mm wide), very good support (libraries, tutorials)
  • minus: quite expensive

WeMos D1 mini (pro)

  • plus: very cheap, USB connector for programming, additional stackable modules (eg. battery charging, TFT screens, motor driver), good form factor
  • minus: no real support (but there is a forum, problems with modules reported

ESP8285 (variant of the ESP8266)

  • plus: really small (!!!) and smart form factor, USB programming and battery charging, optional sensors on board (but no motion sensors)
  • minus: quite expensive, only 1MB memory (nevertheless enough for a lot of application)

For our project we selected the WeMos mini cause we get almost everything we need:

  • USB connector for programming
  • module for battery charging
  • module for a motor driver
  • good form factor (eg. to be put in a vibrator handle or in the base of a dildo)
  • cheap, fast delivery

But there is no shield for motion detection (accelerometer,gyroscope). So we have to use an additional board eg equipped with the MPU9250.

But there is a problem with the WeMos motor shield: After a few seconds it stopped working. And in addition the MPU9250 stopped working, too. Hours and hours we tried different configurations, changed the libraries … The problem was the motor driver shield itself. Fortunately there is an easy work around. Read here.

Another issue is the battery shield. It has an extra USB connector for charging the battery. So you have two USB connectors (one for battery charging and one for uploading). Two USB connectors are not handy. Fortunately we can do without the USB connector for uploading as it is possible to update the software over the air (OTA) using WiFi.


As the body interaction philosophy uses motion for controlling the device we have to add the MPU. Again we use the MPU9250 which has an accelerometer, gyroscope and magnetometer.

Another insight was that you need at least a switch for rebooting. As we want to mold everything the switch must meet the IP67 requirements, which means it is water- (and silicone) proof. If you don’t want to mold the electronics you can use the RESET button on the WeMos mini board.

A perfect basic node has a wireless charging option, too.

Material list for the basic node:

  • Wemos mini board
  • Wemos motor driver shield
  • Wemos battery shield
  • Wemos prototyping board
  • Wemos set of pins
  • LiPo battery (eg. 3,7V 650mAh, 2C, JST plug, available at ebay)
  • MPU 9250 board (for motion control)
  • 1 or 2 encapsulated vibration motors, 3V, available at Alibabaexpress
  • Optional: Switch IP 67 protected (eg. Cherry Switches DC1C-K8AA IP67) – for molding
  • Optional: Wireless charging receiver 5V eg from Seeed Studio

Material: battery shield, Wemos mini ESP8266, motor shield, MCU9250 (first row), LiPo battery, switch, vibration motor (second row)


Soldering the basic node

We use one connector (part of the Wemos set of pins) to connect the Wemos mini with the battery shield and the motor shield. This is done to save space. If your application has enough space you would use one connector for every shield.

Battery shield, Wemos mini ESP 8266, motor shield (from top to bottom)

Now have a look at the bottom side where the motor shield should be. We can connect up to 2 motors. Solder motor 1 to A1 and A2. Motor 2 has to be soldered to B1 and B2. In addition we need input power for the motor. We just use the 5V provided by the Wemos mini battery shield. Connect 5V to VM and GND (from the pins) and GND. But you could use other (more powerful) power sources, too.

Wemos offers a prototyping board. We use it for mounting the switch and for the MPU9250. Connect the MPU9250 to the bottom side of the prototyping board. Therefore 4 pins have to be soldered

Solder pin (1 row, 4 pins)  on the top side next to TX, RX, D1, D2


Now look at the bottom side of the prototyping board. Put the MPU 9250 so that VCC, GND, SDA, SCL are connected to the pins.

Next, solder the MPU 9250.

Then add more pins to the prototyping board at both sides. The picture shows the bottom side of the prototyping board.

Now wire the prototyping board. The picture shows the top side.

Now you can add the switch. Place it in the middle of the board on the top side. Connect GND and RST to the switch. Now you have a switch for rebooting which can be molded.

Now we have both parts ready and can stack them together.

Stack them together!

Now add the LiPo battery, which should have a JST header. Now your basic node is ready.

Wireless charging option

Especially for sex toys a wireless charging option is reasonable as this is a requirement for silicone molding of the toy.  And when the toy is molded it is safe and washable.

The wireless charging module consists of a sender (or transmitter module) and a receiver module. You have to solder the receiver module to the battery shield. Don’t mix the modules.

unfortunately there is only  a USB connector. If you don’t want to remove the USB connector you can solder the red (+) wire to the R330 resistor as shown on the pictures. The black (-) wire can be soldered to any pin labeled (GND).

Now put the receiver module on top of the battery module.

Now stack the protoytping board on top of the battery shield.  And connect the battery.To charge the battery connect the sender (or transmitter) module to 5V. To power the sender module you may use a USB port power source which has about 500mAh or more. Place sender and receiver coil about each other.  For a more professional charging solution you need a charging station. The making of a charging station using 3d printing is described here.

Learn how to construct the mold form in part 2:

part 2: Molding the basic node

part 3: Software for the basic node

OpenSCAD as silicone molding form generator

scadmoldform1tryballs_revisited_3_finalAn alternative to 3d-printed sex toys are silicone toys. For making such a sex toy you need a molding form, where you pour in the silicone. If you use Tinkercad to build the form for the balls motive, you may need more than one hour. If you are not experienced in 3d constrcution it may take days. That’s ok and can be fun as you can realize your fantasies step by step.



molded-with-ueberh-querBut if you want to change a detail or want to resize some parts of it, it will take a long time as you have to unbuilt parts of the form, make changes and then reassemble. Sometimes building from scratch is faster.

In the last blog post we have introduced OpenSCAD to construct a sex toy form. Now we want to build a hull for the sex toy for overmolding.

The basic idea is very simple:

  • Generate two forms. The smaller one has the size of the sex toy you want to make. The larger one will be the form where you pour in the silicone.
  • Than use the OpenSCAD difference command which “subtracts” or cuts out the smaller form from the larger form.

But it is more complicated:

  • You have to include a frame otherwise the form would fall over.
  • You need two forms (A and b) so you could open the form after molding.
  • Both forms must be fastened together when molding. Therefore you need holes for tinkering wire.

bi-round-12-scadWe have created a solution for molding form generation which is as flexible as our OpenSCAD sex toy generator. In addition you can change the thickness of the frame. Therefore you have to change the variable frame_thickness.

The SCAD script uses the module base which is already introduced. The generation of the frame is done in the module frame. The frame consists of a base plate and two supporting frames which stabilize the whole form. In addition there are extensions to the frame in the upper part of the form. These extensions will provide holes for fastening both forms.

The module complete_form constructs the form which is tricky. The union command is used to join the complete outer form and the frame. Now we have a filled form and have to remove the inner part. This is done by subtracting another complete form which is a bit smaller than the outer form. This is done with the difference command.

Another module hole provides all holes for the tinkering wire. At last we construct part A and part B of the molding form. Again the difference command is used to cut out one half of the form. This is done by subtracting a cube which is placed in the middle of the complete form. In addition the holes must be subtracted from the complete form.

You can build in the body interaction vibrator development board to make a vibrating dildo, controlled by motion or by another body interaction vibrator development board. Read more here.

Try out with the Thingiverse customizer.

Download the zipped SCAD file here: bi1-round12

Or copy and paste the source code to the SCAD software:

// bodyinteraction toy form and mold form generator
// radius of bottom part
r_bottom=25; // [15:5:80] 
// height of bottom part
h_bottom=30; // [10:5:80] 
// top rounding of bottom part
rounding=10; // [10:5:20]
// radius of ball 1 
r_ball1=21; // [15:5:50] 
// radius of ball 2
r_ball2=15; // [15:5:50] 
//radius of ball 3 
r_ball3=11; // [15:5:50] 
// radius of connecting cylinders
connector_radius=8; // [10:2:20]
// distance between balls and bottom part
ball_distance=15; // [10:2:40]
// offset (thickness of hull)
// thickness of frame

height=h_bottom+3*ball_distance+r_ball1*2+r_ball2*2+r_ball3*2; echo(height);

// form part A
difference() {
//form part B
difference() {

module holes (height,h_bottom){
for (i=[h_bottom+30:10:height])

for (i=[0:10:h_bottom+20])

for (i=[h_bottom+30:10:height])
for (i=[0:10:h_bottom+20])

module complete_form (r_bottom,h_bottom,rounding,r_ball1,r_ball2,r_ball3,connector_radius,ball_distance,o,frame_thickness,height) {
 difference() {
 union() {
 //complete frame

module frame(width,o,height,frame_thickness,r_bottom,h_bottom,rounding) {
 translate([-width/2,-width/2-2*o,height]) cube(size=[width,width+2*o,frame_thickness]);
 translate([-width/2,-frame_thickness/2,0]) cube(size=[width,frame_thickness,height]);
 //frame 1 extensions
 translate([-width/2-010,-frame_thickness/2,-5]) color("blue")cube(size=[12,frame_thickness,60]);
 translate([-width/2-10,-frame_thickness/2,55]) color("red")rotate([0,45,0]) cube(size=[12,frame_thickness,20]);
 translate([+width/2-2,-frame_thickness/2,-5]) color("green")cube(size=[12,frame_thickness,60]);
 translate([+width/2+01,-frame_thickness/2,47]) color("green")rotate([0,-45,0]) cube(size=[12,frame_thickness,20]);
 translate([-frame_thickness/2,-width/2,0]) cube(size=[frame_thickness,width, ,
 // stabilize bottom with cylinder
 cylinder(h=r_bottom*2-rounding*.5, r1= r_bottom-rounding, r2=0);


module base (r_bottom,height,rounding,connector_radius,ball_distance, c1,c2,c3) {
 union () {
 // connector
 color("DarkSlateBlue") cylinder (h=height-0,r=r_bottom-rounding,$fn=60);
 color("MediumSlateBlue")cylinder (h=height-rounding,r=r_bottom,$fn=60);
 translate([0,0,height-rounding]) color("SlateBlue") rotate_extrude() 
 translate([r_bottom-rounding,0,0]) circle(r=rounding,$fn=120);
 // circle (ball) 1, 2 and 3
 translate([0,0,height+ball_distance+c1]) color("Indigo")sphere(r=c1,center=true,$fn=60);
 translate([0,0,height+2*ball_distance+2*c1+c2]) color("Violet")sphere(r=c2,center=true,$fn=60);
 translate([0,0,height+3*ball_distance+2*c1+2*c2+c3]) color("Purple")sphere(r=c3,center=true,$fn=60);


Go to the first part of the SCAD tutorial

New vibrator design “fusion”


fusion-quer-look-throughbodyinteraction designed a lot of vibrating toys, some are usable as massage devices, some are explicit sex toys (vibrator ring, balls), some are experimental (collar). Everyone is motion controlled. If you have more than one they will influence each other remotely, eg. a vibrator and a vibrator ring.


But a device like a classic big vibrator is still missing. So we designed the “fusion” which is approx 19cm long and up to 4+cm in diameter. It is called fusion as the case is made of silicone and 3d printed material (ABS).


We have put the body interaction vibrator development board, motor and battery in a silicone form. There is an on/off switch – so when you travel the vibrator doesn’t wake up when it is moved. And you can charge the battery with a USB micro connector. There is a spacious inlay for the electronics, so it will be easy to get it done.


  • easy to charge the battery via USB
  • on/off switch
  • hard handle
  • flexible upper part
  • large (if you like this)
  • ISP interface (“hacker port”) accessible


  • only the silicone part of the form can be put under water for cleaning

What do you need?

  • 200 ml silicone with high shore A rate, eg. shore A 45 from
  • optional: special colour for silicone molding
  • 3d print of the molding form, inlay and closure
  • tinker wire
  • body interaction vibrator development board with LiPo and motor (or similar Arduino boards)
  • bin for preparing the silicone, something to stir the silicone

How much is it?

  • Board, battery, motor: 30$ (buy at Tindie)
  • Silicone: 10$
  • 3d Prints: less than 5$

Step by step instructions

Step 1: Print out the inlay, the form and the enclosure


Download as zip-file: Fusion

Download at Thingiverse:

Step 2: Prepare the inlay: Insert the body interaction board and the LiPo battery

The body interaction vibrator development board is inserted into the provided rails. It it doesn’t fit in use a file to remove printing artefacts. Use some glue to fix the board. Then insert the battery and fix it.

Important: The Micro USB connector must be above the upper part of the inlay.

inlay with description

Step 3: fix the wires of the vibration motor

The vibration motor will hang down from the inlay as the inlay will be put in the form upside down. You can influence the position of the motor by shortening the wire or fixing the wire to e.g. to the battery. In this case the wire of the motor was threaded between battery and board. Therefore the  motor will be in the middle of the vibrator.

inlay-inner-partfusion-looking-through-2in the center there is the overmolded vibration motor

Step 5: Prepare the form

Use some tinker wire to “press” both parts of the form tight together.molding-form-emptyUse some wax to fix little holes in the form where the printer failed. (These are the white spots)


Step 6: Insert inlay into the form

There must be some space between inlay and form for the silicone.

Remark: The two wedge like forms at both sides of the inlay help to hold the inlay. The wedge can be removed after molding.inlay-in-molding-form

Step 7: Cast the silicone

Prepare the silicone as the producer recommends. It takes some time to pour the large amount of silicone into the narrow form. The silicone we use must be used within 10 minutes. So start at once after preparing the silicone.

Important: The USB micro connector, the switch and the ISP connector shouldn’t be dashed with silicone. If this happens remove the silicone. Maybe some silicone will remain behind. This can be removed later when the silicone is solid.molded

The battery is covered with silicone, the USB connecor and switch are not.drying-seen-from-top

Step 8: Remove the form

Remove the tinker wire. Remove overhanging part of the silicone. Carefully tear both parts of the form away. You can use a knife, but be careful not to “hurt” the vibrator. Remove overhanging silicone at the vibrator. Also remove the two wedge like forms at both sides of the inlay.

unboxing-fusionfusion looking through complete

Step 9: Install the closure

Now you can put the closure on the inlay. Fix the closure with glue. (Be careful! The USB connector is not very strong.) closed-inlayround_something_055_final_cap_onlyfusion-closure

Tinker, share and download from Tinkercad:

form and inlay:


Download as zip-file: Fusion

Download at Thingiverse:


New fusion 3d printed and silicone molded vibrator

fusion tinkercadThis is the initial design. The round curved form will be in silicone with vibration motor within (vibration motor not shown on sketch). The red part is 3d printed. It is the enclosure for the body interaction vibrator development board and LiPo battery. You can plug-in the Micro USB connector for battery charging. In addition there is an on/off switch e.g. for travelling.

Update for “balls revisted” – silicone molded vibrator

balls-revisited-v3-wit-v4-inlay-blueThe “ball revisited” silicone molded vibrator uses a wireless charging module. Unfortunately there are different version available. The version with some textile like cable jackets have a different inner radius of the receiver have changed the mounting on top of the picture as this type of the receiver coil needs a little more space. In addition the encasement is a bit larger. new-inlay-seen-from-side-BThere is enough space for the body intercation board (top), wireless charging board (right) and the LiPo battery (below).new-inlay-seen-from-side-BFinally the wire of the vibration motor is glued in the middle of the follow the “old” instruction – nothing has changed. When printing out the 3d parts use the new version 4 of the inlay. All 3d printing STL files at Thingiverse


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