Automatic Fragrance Dispenser

A cheerful idea to fragrance your room without burning is to use an electric/electronic fragrance dispenser. So simply build the automatic fragrance dispenser presented here and place scented crystal rocks/fragranced crystals in the chest and voila you have a wonderful home-brewed automatic fragrance dispenser enough to scent a little room. You can also refresh your fragrance crystals by simply adding additional fragrance oils to make the aroma lasts for several weeks, depending on the encircling environment!

The pricey thing is that now you can comfortably purchase wall-mountable automatic fragrance dispensers online (see below). It’s a quick process – you will be up and going within minutes of opening your web browser. But where’s the fun in that? If you’re always building circuits up, then go through the rest of this article (after learning, it’s a very short process to get started). Else stop here!

Decided to play along with the poor man’s edition? Well, you’re a great walker! First of all, it’s worth noting that I’ve used a simple (and cheap) trickery for this belittled do it yourself project. And it’s only a humble jump to assist you to build your own cheap and cheerful automatic fragrance dispenser using a few parts laying around (you can ofcourse ameliorate a lot yourself).

Frankly, this project idea is in fact an elaboration of one old idea I worked on before a couple of years. It’s simple – dispersing the aroma using one cheap brushless dc cooling fan placed at the top of a common mason jar, filled with enough scented crystal rocks. This time I added a cyclic timer to drive the cooling fan and tweaked it somewhat to run on a standard USB power supply.

This is the entire schematic (v1) of my (poor man’s) automatic fragrance dispenser controller:

At the heart of the fragrance, the powerhouse is a 14-stage binary ripple counter with an on-chip oscillator buffer – the HCF4060BE (IC1). Here, it’s configured as a simple cyclic timer i.e. the timer will energize the brushless dc cooling fan for a finite time, and it will do so repeatedly at regular intervals. In principle, you can configure the length of time it will take for any given output pin (Q4-Q14) to go high. If you wire the “drive” jumper to that output pin, the fan will run for a period of time, length of which is set by the values of C4 & R4. Ideally, C4 should be a non-polarized/bipolar capacitor but a regular electrolytic capacitor will work if it doesn’t leak too naughtily in the reverse direction.

In short, the HCF4060BE contains an easy to use astable, or oscillator stage, followed by a 14-stage binary counter/divider. Pulses from the astable are passed to the binary counter (not all of the outputs of the binary counter are available externally). Pulses at Q4 output (pin 7) are divided by 2^4=16 compared with the initial astable frequency while at the final output, O14 (pin 3) are divided by 2^14=16384 compared with the initial astable frequency. The practical range of values for R4 is from 1KΩ to 1MΩ, while C4 can have any standard value from 100pF upwards. Within these constraints, the frequency of the astable pulses is given by f= 1/2.2 x R4 x C4. Coming to the default design configuration, the estimated base frequency fosc is 0.455Hz.

Although the “heartbeat/ready” and “active” LEDs (LED1 & LED2) add a bit of luxury to the fragrance dispenser, they’re not absolutely necessary to the operation of the core electronics. You can leave them out if you wish. Likewise, the S8050 fan driver transistor (T1) can be replaced with any other suitable NPN type which can neatly handle the drive current requirement of the brushless dc cooling fan wired across the switch output (SWITCH O/P) of the circuitry. My breadboard prototype, powered by a USB power bank, was tested with a 12VDC/150mA 80mm PC cooling fan (Yes, 12VDC) laying on the workbench.

To keep the overall construction sweet and simple, prepare the core electronics circuit on a small piece of veroboard preferably with a socket for IC. One of the easiest ways of modeling the build is to employ a solid mason jar as the enclosure. The 80mm cooling fan can be permanently attached to the lid of the mason jar. First off, make a large (~70mm diameter) vent hole on the lid with a pointed power/hand tool or hot blade (see the template below).

The layout is not critical, however, the cooling fan should be mounted aright so that the airflow is directed towards the top.

Yup, now you have a specially designed automatic fragrance dispenser which is nothing but a small cooling fan driven by a portable power source. Coupled with a configurable cyclic timer, consistent fragrance release is ensured over a period of time. Remember, you don’t just have to mount the device on a wall. Because of the environmentally friendly dry refill, the dispenser can be used anywhere – use it on your desktop, cupboard, window sill, side table, or under a table. It can be moved freely from room to room. Similarly, you don’t need to run the device throughout the day for constant fragrance delivery. Simply switch on your ‘scent machine’ for a little time when you’re in need of a cleaner smelling air, let the cyclic timer to complete a few cycles, and then switch off it – that’s decent!

Needless to say, the default fragrance delivery time period is in seconds but you can reconfigure the design to lengthen the period of time (not tedious, if you know how to play with the chip). A far greater level of accuracy is, however, not compelled in this hobby-level do it yourself project.

List of components

IC1: HCF4060BE
T1: S8050
D1: 1N4007
LED1: Yellow/Amber 5mm
LED2: Green 5mm
R1 & R4: 100K ¼ w
R2: 4K7 ¼ w
R3: 1M ¼ w
R5: 1K ¼ w
R6: 1K2 ¼ w
C1: 100uF/16v
C2 & C3: 100nF
C4: 10uF/25v (non polar)
FAN: 80mm, brushless dc computer cooling fan 12VDC/<250mA (using a 12VDC computer cooling fan at 5VDC slows it down but conserves the scented crystals)!

Finally, as clearly pointed before, this design is based on generally available low-cost electronics components, and I tacked together my breadboard prototype with components taken from the junk box. While gearing up this article, I was informed by a prominent online seller that the HCF4060BE IC is no longer available as it’s discontinued by ST. Don’t panic, you can still try the drop-in-replacement part NTE4060B (http://www.nteinc.com) in case of any difficulty in gathering the proposed HCF series IC. Another similar chip to consider on this point is the HEF4060B from nexperia (http://www.nexperia.com).