Analumi-Clock V2

An analog clock with no hands (well not in the standard sense), rather the hands are virtual and created by the effect of UV light on photo luminescent material. Hence called an Analumi-Clock. (Analogue Luminescent Clock)

This is a revision of the Analumi-Clock. Why a revision.

Well the first version was more a case of having a working design rather than how it looked.

Therefore, the look was given more consideration in version 2, this is in addition to a number of other changes.

In the original version the housing was simply to conceal the electronics but left the display exposed which made it vulnerable and given the size and positioning of the housing compared to the display made it somewhat disjointed. This style also meant that it was only really suitable for shelf mounting were there is less chance of impeding the display.

The new enclosure started life as a floating shelf which seemed ideal in many ways. It could be mounted in a number of ways; shelf, wall or table and would support both the display and house the electronics. It's minimalist clean lines also fitted in well with a clock with no physical hands.

One of the changes in the electronics was in the servo driver board.

There is a requirement to switch off individual LED's to differentiate between the hour and minute hands.

The original servo driver board was chosen due to its lower cost and small size but was later found it would not allow independant switch off of a channel used to control an LED, the LED was always on, although intensity could be varied. This therefore required some means of switching off the required LED and was accomplished by adding a MOSFET pulldown circuit. This workaround still enables the cheaper board to be utilised.

However, changing to the board used in the Lumi-Clock simplifies build and control, enabling easier modification of hand configurations without recourse to additional boards.

The other change removes the Pinbetween.

The LED arm was modified to reduce its overall size and also to remove the Hall effect sensor from the front to improve the asthetics. The Hall effect sensor was moved to the motor board at the back and the disc flange modified to accomodate the ball magnet at this new location.

Different methods of photo luminescent display were evaluated both opaque film and translucent filament.

In this case opaque film has the following advantages, brighter and slower decaying light emission, improved resolution leading to better visibility under higher ambient lighting conditions for longer compared to a filament disc.

This project was listed in the top ten of All3DP's Mightiest Micro:bit Projects of 2024 published March 29th 2024

Microbit V2 (preferred due to built in speaker, V1 will work but will require an external sounder.)

Compact Robotics Board

5V stepper motor with ULN2003 driver board (Note: Similar motors exist with the same footprint, size, mounting and connector. However, the phases may not be connected the same resulting in unpredictable operation.)

DS3231 RTC

Micro USB to 5V breakout

Jumper Jerky F/F - Qty 9

Jumper Jerky Junior F/F - Qty 20

Jumper Jerky Junior F/M - Qty 2

Pin Header right angle - 24 pins

Pin Header straight - 8 pins

Straight 2 row headers (7 x 2), 14 pins

Hall sensor

20pin DIL IC socket

Resistor 10k 

Resistors 220R - Qty 8

Capacitor 100nF MLC - Qty 2

74HC541 Octal Buffer IC

Stripboard

LED UVA 3mm - Qty 8

Switch SPST

Push Button Momentary Switch - Qty 2

3 pin terminal block, 2.54mm pitch

22 SWG tinned copper wire

Screws M2

M2 Bolts 16mm - Qty 12

M2 threaded spacers 5mm - Qty 11

M2 self tapping 8mm - Qty 4

M2 self tapping 12mm

Bolts M3

M3 Bolts 8mm - Qty 4

M3 Bolts 6mm - Qty 16

M3 Bolts 25mm - Qty 6

Hex standoffs M3

M3 Hex spacers 5mm - Qty 8

M3 Hex spacers 10mm - Qty 2

Hex standoffs M4

M4 Hex spacer 5mm

M3 x 20mm self tapping screws - Qty 5

3d Printer

Filament

Luminous Paper

Compact Disc (CD) 120mm or template (card/plastic), with the same dimensions.

Ball magnet 3mm

PCB mounting block - Qty 4

Stretcher Plate 38mm

Wire wrapping tool for 30 AWG wire

30 AWG wrapping wire (ideally the same colour as the dial).

May prove more cost effective to buy a range of values rather than individual values unless you already have them available. Some components may also have a MOL greater than the quantity specified in the component list.

No affiliation to any of the suppliers used in this project, feel free to use your preferred suppliers and substitute the elements were appropriate to your own preference or subject to supply.

Links valid at the time of publication.

1mm drill bit

2mm drill bit

3mm drill bit

4mm drill bit

8mm drill bit

38mm Hole dril bit

Countersink drill bit

Drill

Saw

Clamps

Ruler

Combination Square

Allen Keys (3mm & 4mm)

Pliers

Soldering Iron

Solder

Sanding paper

This project makes use of Photo Luminescence using film layered with Strontium Aluminate which has a green glow although different mixes can result in different colours and persistence.

Once charged, light from the film will continue to be emitted after the charging light has been remove. The charging light in this case comes from UVA LEDs.

The light emitted after charging is initially very bright but quickly decays to a lower intensity becoming further deminished over time, this persistance can last for several hours but may only be fully visible in total darkness. If the film is exposed multiple times in relatively quick succession then multiple ghost images will be present. Therefore, to minimise this effect a delay is applied between successive exposures.

Consequently, this project is best viewed in a low light environment.

UV LED's are used to illuminate the luminous film but require some means of moving the film under the LED's to create the hands.

This is achieved by using a single stepper motor which can rotate clockwise and anti-clockwise.

Fitted to the stepper motor is a CD or similar disc and to this is fixed the luminous film.

A fixed arm is at the 6 o'clock position and to this 8 LED's are attached to form one column.

As the motor rotates the luminous film moves under the arm pausing momentarily whilst the required number of LED's for the appropriate hand are switched on.

Each hand is created in turn with the appropriate angluar offset resulting in both hands coming to rest at the required positions for the analogue time being displayed.

Control is provided by a Microbit in conjunction with a RTC, servo board and bespoke logic.

The LED arm, dial and motor support are 3D printed.

The coding was carried out using Makecode for MicroBit.

The main difference between the code in the original Analumi-Clock and V2 is in the control of the UVA LED's due to the use of a different motor control board.

The delay between time updates is controlled by the value of the passing parameter in the long_dly procedure.

This is set to update the display once every 60 seconds.

The main part of the process is in controlling the stepper motor to position the "hands" in the correct position to emulate a traditional clock. But there is only one positional element and not two separate physical hands.

Part of the process is defining a known reference start point.

In this case the reference is the 6 o'clock position. At this fixed position is situated the Hall effect sensor.

The Hall effect sensor detects the presence of the magnet attached to the rotating Disc Flange which is attached to the stepper motor.

The time setting is defined in two parts for the elements hours and minutes.

The first part is to home the Display to a known start position, this process is carried out in the homing procedure.

"homing", by rotating the Display until the magnet is detected by the Hall effect switch at which point the motor is stopped.

The output of the Hall effect switch is connected to P0 which is configured as a digital input.

A while loop checks if the digital pin=0 meaning the magnet is aligned with the sensor. Therefore, Home = True

If the digital pin=1 the loop continues, however to prevent an endless loop a 60 second time out is assigned.

If the timeout is reached, Home = False.

Whilst in the while loop and checking the status of the sensor the motor is being turned.

In order to rotate the motor we apply a step pattern, the 8 step pattern is held in beat_list.

Calculate Steps for Hours and Minutes.

360/step angle * gear ratio = 360/5.625*64 = 4096step/rev = 0.088deg/step

Using an 8 beat pattern = 4096/8 = 512step/rev = 0.703deg/step

512/360 = 1.4222 steps/deg small enough step for our needs.

360/60 minutes = 6deg/min

360/12 hours = 30deg/hr

As the clock is in 12H format and the time from the RTC is in 24H format, subtract 12 if Hr >12

Steps/Hr = int(((Hr+(Min/60))*30)*1.4222)-256 [Add minutes allowing hour hand to move smoothly between intervals]

Steps/Min = int((Min*6)*1.4222)-256

Degrees = Steps/1.4222

[One revolution is 512 steps and half a revolution is 256, Therefore, 256 is subtracted because the reference is at half a revolution. Hrs = 6 o'clock or Mins = 30 minutes]

The steps returned can be positive (anticlockwise rotation) or negative (clockwise rotation).

Examples:

6 o'clock = 6hr 0min

Hour Hand = 0 steps = 0 degrees, Minute Hand = -256 steps = -180 degrees

6:35 = 6hrs 35min

Hour Hand = 24 steps = 17 degrees, Minute Hand = 42 steps = 29 degrees

3 o'clock = 3hr 0min

Hour Hand = -128 steps = -90 degrees, Minute Hand = -256 steps = -180 degrees

9 O'clock = 9hr 0min

Hour Hand = 128 steps = 90 degrees, Minute Hand = -256 steps = -180 degrees

Anticlockwise = Steps*8 step pattern. See procedure anticlk.

Clockwise = Steps*8 step pattern in reverse order. See procedure clkwise.

The basic process is

Home the Display.

Rotate the Display to the required Hour position.

Flash the Display with 6 LED's for 1 second.

Home the Display.

Rotate the Display to the required Minutes position.

Flash the Display with 8 LED's for 1 second.

Home the Display.

Wait 60 seconds and repeat the process.

The schematic shows how the different elements are connected.

The Microbit plugs directly into the motor board.

The RTC uses pins 19 & 20 and 3V and 0V. A backup battery is required to retain the time if power is removed.

The stepper motor used comes complete with a ULN2003 driver board (with visual driver bit indication), and is connected to pins 13, 14, 15, 16, 5V and 0V. This rotates the Display disc in front of the UVA LED's.

The Hall sensor using pins 0, 0V & 3V and is used to reference the home position for the Display disc

LED driver which is connected to 0V, 5V, Servo outputs 1 to 8 & Microbit pin 1 and the 8 UVA LED's to create the hands.

The majority of connections are made using jumpers to interconnect the various boards.

However, some soldering is required to build the LED driver and mount the LED's and Hall sensor.

Using a CD (alternatively stiff card or plastic), as a template draw around the perimeter of the template and the centre hole onto the luminous film. 120mm diameter, centre hole 15mm diameter.

Then cut around the perimeter line and centre hole using a sharp blade.

The resulting Display Disc will be stuck to the CD with double sided tape or a suitable glue, some luminous films are self adhesive simplifying the task.

If using glue test the effect on a sample of the film to ensure it does not damage or mark the film or effect the lumosity.

I simply ran a bead of glue around the surface close to the outer perimeter, no need to cover the entire surface as the central portion of the Display Disc is clamped by the Disc Flange.

Hold the luminous film in place with small slithers of tape applied around the edge and hold it flat with a weight (heavy book), until the glue has dried.

The Hall effect sensor is omnipolar, meaning it will respond to either magnetic polarity.

The 100nF capacitor is for noise decoupling.

As the sensor will be fitted on the motor board and the motor driver and motor will also be fitted to this board, less space being available the sensor connections were made directly without an intermediate connector. When powered and in the abscence of a magnetic field the output is High when a magnetic field is detected the output goes Low.

The UV LED's are not driven directly by the microcontroller.

We will make use of the motor board which has 16 servo outputs although only 8 will be used, this will allow us to control each LED with PWM. Although, it will only be required to switch them fully on or off individually.

Due to low drive capability a buffer IC rated up to 7.8mA per output is used to drive the LED's from a 5V supply.

The IC is a Non Inverting Octal Buffer with TriState outputs. In this case the IC is mounted on a piece of stripboard (18 holes by 16 strips), in a IC socket.

Right angle pin headers are used to make the connections for inputs, outputs and power.

With one decoupling capacitor on the supply and a pull up resistor to pin 19. When this pin (19), is low the outputs follow the inputs and when high the outputs are high impedance and disabled. This pin is driven by the microcontroller on P8

This board is fitted under the motor board.

The centres for the fixing holes are marked by a single cross in the corners on the stripboard, cuts are included to isolate the corner when using metal standoffs.

The holes are made with a 3mm drill and attached to the base board on M3 x 5mm standoffs.

The 74HC541 in a DIL package was difficult to obtain at the time of writing but a TSSOP package variant is available. However, this necessitates a SMT breakout PCB and SIL sockets to implement directly on the stripboard in the absence of a custom PCB for the entire circuit.

Alternatives using FET's, BJT's, 74AC244 or if you don't mind losing one of the LED's the ULN2003. Which ever method is used ensure the LED's are suitably wired for correct operation.

The elements to be 3D printed were designed using BlocksCAD but are also available on TinkerCAD.

The motor support which holds the motor at the correct position has been modified to remove the feet and to add the cavity for the Hall sensor. No requirement for feet as this will be mounted to the Display board.

LED Arm (Hall sensor cavity removed), which supports the LED's with integral dial with hour markers. The dial has been modified to enable M2 bolts to be fitted at the hour markers both for highlighting and to enable fixing.

The Display Disc flange which fixes to the CD and the axle which fixes the hub and the axle to the motor. This has been modified to add the ball magnet cavity on the rear Disc Flange.

Elements are printed using PLA at 100% infill, layer height 0.15mm.

They can be printed individually or all together (fitting within the perimeter of the dial).

The shield was added later to cover the wiring to the LED's.

Amalumiclkdl3min is an update to include minute/hour markers these are includede on boths sides of the dial.

Tinkercad file links.

tinkercad.-analumishield

tinkercad-analumiaxle

tinkercad-analumirg2

tinkercad-analumidsc

tinkercad-analumimtrn

tinkercad-analumiclkdl3

Analumiclkdl3min | Tinkercad (updated dial)

The 3D printed motor support has all the holes to mount the motor and fix it to the Display board using M3 bolts.

In addition to mounting the stepper motor it's driver board is also fitted to this board below the motor, the driver board is secured with 4 bolts.

The Hall sensor is also attached here.

The LED arm is located at the 6 o'clock position to which are fitted the 8 UVA LED's plus the integral dial and connector foot.

The dial is a close tolerance fit to the display disc therefore ensure that the internal surface of the dial is free from aberrations

The dial is pre-printed with depressions and 2mm holes at the hour intervals.

The connector foot is pre-printer with holes to enable the 2 row pin header to be fitted and enable attachment to the display board by 2 x M3 bolts.

The updated LED Arm/Dial includes minute/hour markers on both the front and back of the dial.

The Axle requires an M4 X 5mm Hex spacer.

Apply a little glue in the hex hole and push the spacer in to the hole and allow the glue to cure.

If the hex spacer protrudes above the surface sand or file this flat to the surface to maintain a level fit to the Disc Flange.

The other end of the Axle is a push fit on to the stepper motor spindle.

The Disc flange consists of one disc and a ring.

The disc fits at the front of the CD and the ring fits at the back.

With the disc face down and the CD sandwiched between this and the ring, centre the disc and ring on the CD and place the axle in the middle.

Mark the two holes in the ring through to the CD and drill out using a 3mm drill bit.

Fit two M3 X 6mm bolts through the sandwhich and tighten, the holes in the disc and ring are tight by design negating nuts.

The axle fits in to the depression at the back of the disc flange and is held in place with a M4 x 6mm bolt.

The Display flange ring contains a depression into which fits a 3mm ball magnet which is glued in place.

This is used in conjunction with the Hall sensor to determine the discs position and define its start reference.

The 8 UVA LED's are air wired to a 2 row header and fixed to the arm by the common ground wire with M2 x 8mm screws using the pre-printed holes the series resistors are fitted to the LED Driver to simplify layout.

The LED's are configured as common cathode.

Rather than directly soldering the connections wire wrapping was employed to keep the wiring tight and neat.

The pre-printed holes are enlarged with a 1mm drill bit and the header is a press fit into the LED arm via the short terminals. Solder connections would make the terminal ends larger making insertion difficult.

However, once the terminals are wired the 2 row header can held firmly in place in the LED arm with glue or carefully applying a soldering iron to the terminal ends to flow the plastic.

Be sure to connect the LED's the correct way round.

The display board is made from black Acrylic with dimensions 170mm(W) x 170mm(H) x 5mm(T).

In the centre of this is cut a 38mm diameter hole.

Align the centre hole with the axle hole in the motor support and mark the position for four holes using the motor support as a template, drill the holes with a 3mm drill bit then countersink the holes on the forward facing side.

The motor support fixes to the display board with four M3 x 25mm bolts and 5mm hex standoffs.

These bolts align with the holes on the motor driver PCB and are held in place with 4 x M3 nuts.

Between the bottom of the base board and 5mm up from the display board edge is a space into which a slot will be made through which the connector for the LED arm will protrude in addition to two 3mm holes for stability.

Attached to the LED arm is the clock dial this is fixed to the display board with 2mm bolts positioned at each of the hour intervals. This is used as a template to enable the 2mm drill holes to be made in the display board.

In each corner of the display board is drilled a 3mm hole which aligns with the PCB mounting blocks. These are attached with M3 x 12mm bolts.

The front of the display board is set back from the housing edge by 25mm and held in place with the PCB blocks.

Each PCB block is fixed with a M3 x 20mm screw, one per corner.

The housing is a floating shelf with dimensions 250mm(W) x 250mm(H) x 90mm(D) using 15mm fibre board, this was purchased ready made. To this would be attached the display board and the base board.

A window will sit in front of the dial to protect it.

Measure 10mm in from the front edge of the frame and 42mm in from the left and right inside edges. At the intersection of these two points drill a 2mm pilot hole and fit two M2 x 8mm self tapping dome head screws, repeat the process on the top inside edge.

Fitting the hall sensor to the motor support.

Take the hall effect switch and bend backwards all 3 leads by 90 degrees, insert all leads through one of the slots such that the sensor sits in the cavity. Making sure the active side is facing forwards.

Apply a blob of glue or tacky to hold the sensor in place whilst soldering takes place to attach the leads and capacitor.

Ensure the leads are long enough the reach the Motor board.

Fitting the motor support to the display board.

Taking the Display board with all the predrilled holes for the Disc flange, corner bolts, Motor support, LED arm and Dial.

Fit M3 x 6mm bolts through the two motor support holes and secure with M3 x 5mm standoffs.

Fit the motor to the standoffs and secure with M3 x 5mm bolts.

Attach the Motor support to the rear of the Display board and insert the four M3 x 25mm bolts and fit the M3 X 5mm standoffs.

Make sure the motor support is centred in the Disc flange hole by fitting the Display Disc to the Axle and push this on to the motor spindle. Adjust the motor and/or motor support to ensure the Disc flange is central and and the Display Disc is level and not touching the Display board.

Fitting the dial to the display board.

Attach the dial with 2mm bolts with the LED arm connector protuding through the slot in the Display board and also fitting the two M3 X 25mm bolts.

Ensure that the Display disc is centred within the dial.

Connect the Motor connector to the Motor driver and push it over the four screws passing through the Motor support and secure with nuts.

If the Motor driver PCB does not easily fit over the screws, slacken the screws a little to create some play, fit and retighten, failing this file lightly with a round needle file were the screw rubs against the hole in the PCB.

Secure the Display board to the housing by the corner bolts.

The majority of elements fix to the board with bolts, standoffs and stacked over other boards were applicable.

The elements attached to this board are LED driver, Motor Board, RTC and USB connector.

The base board is made from Acrylic with dimensions of 170mm(L) x 58mm(W) x 5mm.

Corner cutouts 16mm(L) X 13mm(W) are made to accomodate the PCB blocks.

All holes are made with a 3mm drill bit and countersunk on the bottom side.

Details of dimensions and drill holes are attached

Into the four holes assigned for the LED driver insert four M3 x 6mm countersink bolts and secure in to four M3 x 5mm standoffs. Position the board over the standoffs and fix with four M3 x 6mm bolts.

Attach the eight outputs via leads to the terminals on the LED arm (were LED 1 is topmost on the column and Led 8 is the bottom most on the column), not forgetting the 0V line.

Attach the eight inputs via leads to the Servo outputs (identified by S), numbered 1 to 8 on the Motor board and a lead from 0V (provision is made for multiuple ground connections), to the closest ground connection (labelled G against a Servo).

Fit the two M3 x 10mm standoffs with M3 x 6mm countersink bolts. Position the motor board orientation such that the Microbit display face is visible when inserted and fix with four M3 x 6mm bolts.

Connect P8 on the Motor board to the LED driver on pin 19.

Connect pin 20 on the LED driver to a Servo supply (labelled V).

Connect P13, P14, P15 & P16 on the Motor board to in In1, in2, in3 & In4 on the Motor Driver.

Connect the supply terminal pins on the Motor board to the Motor driver.

Connect the supply screw terminals to the USB connector which itself is attached to the base board by M3 bolts and standoffs.

Connect the Hall sensor output to P0 and the positive supply to the closest Servo supply (labelled V) and the 0V line to its associated pin labelled G.

From the RTC to the Motor board connect, 0V to GND, V+ to 3V, SDA to pin 20 and SCL to pin 19.

The buttons to set hours and minutes and the set enable switch are mounted on a stretcher plate.

The switches to enable setting of the time are mounted to a stretcher plate which just requires the existing cutouts are filed wider.

One of the two pre-existing holes attaches the plate to the base and the other is used to fix the plate to the housing.

The set enable toggle switch uses the horizontal slot and is connected to P1 and 0V.

The hour (P5) and minute (P11) push button switches with a common connection to 0V are mounted in the vertical slot.

To keep the display dust free and protected from any contact that may impede the display disc an Acrylic window is inserted in front of the dial, this is designed to be removable.

Cut a square of clear Acrylic 170mm x 170mm with a saw and remove any burr with fine sanding paper.

Test fit the window to ensure its not too loose, this can be remedied with some tape or a slither of rigid plastic glued to the edge.

Measure 10mm in from the left and right of the top edge and with a triangular needle file make a 1mm notch. Due to the window being a tight fit the notches enable a wire to be inserted to pull the window out when/if required.

The shield was added to cover the wiring to the LED's.

This simply fits over the LED arm and is held in place with a M2 12mm self tapping screw which fixes in the hole at the six o'clock position.

Setting the clock.

Before setting the clock ensure that the RTC has a battery fitted to retain the time when/if power is removed.

The default time format is 24 hour mode.

Move the switch to the set time position a plus symbol will be shown on the display.

Press Button A for Hours. (0 to 23)

Press Button B for Minutes. (0 to 59)

Press Buttons A & B together to set the time, the entered time values will be displayed.

Move the switch from the set position.

At switch on or after setting.

If the clock has been previously set, it will auto home unless it is in the home position already.

Homing for hours will be indicated on the Microbit display with a circle containing a upright bar.

The hour will be displayed on the Microbit.

The dial homes then moves to the hour position and illuminates the LED's.

The minute will be displayed on the Microbit.

It then homes and then moves to the minute position and illuminates the LEDs.

Homing for minutes will be indicated on the Microbit display with a circle containing a right pointing bar.

If the Microbit displays a "X" this indicates a homing error related to the Display disc not moving.

There are a few reasons why the Display disc may not move:

1) The CD edge is rubbing on the inner surface of the dial, remedy by ensuring the inner surface of the dial is smooth, ensure the edge of the CD has no protusions that will rub on the inner surface of the dial, ensure the CD is centred within the dial.

2) The Disc flange is rubbing on the hole in the Display board, remedy by ensuring the surfaces are smooth and its centred by adjusting the axle on the spindle, ensure the motor support is centralised, ensure the CD is horizontal with respect to the Display board.

3) The CD rubs on the LED arm, remedy by ensuring the CD is horizontal with respect to the Display board and not sitting too far forward on the spindle.

Hope you found this revised version in my clock series informative and interesting..

That's all for now until the next time.