Automated Blinds - Alexa Voice Controlled

08-June I had the tolerance for the curved chain guide to gear spacing too tight causing it to bind when printed on some printers. I have increased this distance by 0.5mm which has removed the binding and allows the motor to move freely.
The new STL is called D1-Lid

A  compact self contained voice controlled automatic blind opener for amazon Alexa using an ESP8266 Lolin D1 Mini microcontrolled and a ULN2003 Stepper motor controller with a 28BYJ-48 5volt stepper motor.

Total cost is less than £10 a unit even when buying from Amazon. 

The whole set of components prints with no supports using a 0.2mm layer height and PLA.

The drive gear is for 3.2mm diameter ball and an approximate pitch of 4.5mm chain for my vertical blind system but this could be altered to suit other pitch/Diameter drive chains

The ULN2003 requires a 0.1" four pin male header soldering in the In1-In4 position if your board does not already have them fitted. 

The D1 mini requires a four pin 0.1" female header soldering into the D1-D4 GPIO holes and a positive wire from the 5v pin to the ULN2003 5v and a ground wire from the D1 to the ULN2003

I would suggest shortening the wires from the stepper motor to aid assembly. I made mine 70mm long by cutting the wires and fitting a new plug but you could cut and solder them and insulate with heatshrink tube.

The code uses the D1's EEPROM to store the last commanded position so if the power is reset or the processor reboots the unit will reset to the off position if the blinds were last commanded on. If the blinds were off they will remain in position therefore having a defined starting point for operation.

In the code add your WIFI SSID and password. 

The blindLength variable (4200) is the rotation distance it moves (alter to suit your curtains/blinds) 

The blindDir variable controls the rotation direction either 1 or 0. 

The deviceZero (d1) variable is the name that Alexa will find when searching for devices and will use that to control the blinds. For example saying Alexa, turn on D1 will move the motor to the on position and turn off D1 will close the blinds.

I would suggest setting up a routine in the Alexa app to contol the blinds then it is easier to add more units by simply changing deviceZero to D2, D3, D4.. etc

Assembly is straight forward screwing the ULN2003 down to the case then plugging the D1 mini into the four pin header. Fit the rear support bridge for the board then the motor. The rear support bridge supports the rear of the D1 mini and gives a secure support so the board doesn't move during USB insertion. Fit the top place using couner sunk 3mm bolts, 12mm x2 for the lid and 25mm x2 through the top and chain guide. The gear and knob is a simple friction fit, No fastenings required.

To fit the motor make sure the chain joint is far enough up the chain so it will not get jammed in the gear during operation. Split the chain and feed one end into the gear while turning the knob by hand to feed the chain through. Join the chai back together then gently pull the assembly into the desired mounting position so there is no slack on either side of the chain and then mount to the wall using suitable fixings.

A 1 amp or greater USB PSU will be sufficient. Simply plug it in and tell Alexa to add a device. After that it can be commanded on and off as required.