Introducing a very practical time keeping device for the home and kitchen. The project was developed due to the fact that although there are many different timers in different devices (watches, smartphones, etc.), all of them are not convenient to use in a kitchen or workshop. The controls should be simplified as much as possible - no extra buttons that make it difficult to immediately remember which is responsible for what.
Schematic diagram of a timer with an encoder
Circuit diagram for a kitchen timer with an ATtiny 2313 microcontroller Once upon a time, mechanical timers were on sale - they were really easy to use. So it was decided to combine this simplicity with a modern base. This is how this timer with a regulator - an encoder - came into being. In it, as in the mechanical prototype, you can increase and decrease the countdown time. The basis is the ATtiny 2313 microcontroller. Here's to it.
Timer signet drawing How the device works
The increase/decrease in time occurs abruptly for several seconds at once. In addition, time can be paused.
The last 5 minutes are signaled by short double beeps every minute. And for the last 15 seconds it beeps every second.
It is possible to turn off the current beeper signal by pressing the encoder or turning its knob in any direction.
Side view In order to simplify control as much as possible for the user, the countdown timer does not have any other unnecessary functions.
Side view of parts And instead of recognizing time steps of 15, 30, 60 seconds, it would be better to determine the speed of rotation of the encoder knob and change the time based on this. Slow rotation counts individual seconds, fast rotation counts steps of several minutes.
Ready homemade LED timer The case... It never got around to it 🙁 The timer has been used for a long time in a half-open form: there are 3 AA batteries on the bottom, a three-digit LED indicator on the front, and a time selection knob on top.
Video of timer operation
Here's a video showing how the device works in different modes, with a mechanical stopwatch next to it for comparison.
In the culinary art, maintaining the accuracy of time plays no less important role than the accuracy of following the recipe. This timer is designed specifically for use in the kitchen, it is very easy to use and allows you to set any time delay in the range from one minute to 99 minutes, in steps of a minute, by rotating the handles of two switches. The end of the set time interval is indicated by a tonal, fairly loud sound signal that sounds for one minute (if not turned off earlier).
The timer is not intended to control electrical appliances; its task is to inform the cook that the cooking time has expired.
The circuit diagram is shown in the figure above. There are only three counter chips of the K176 series. D1 is a clock chip, in this case it produces minute pulses and a pulse signal with a frequency of 1024 Hz, which serves for sound indication. D1 contains two counters, the first lower one produces, along with other signals, pulses with a frequency of 1 Hz, and the second upper one contains a divider of these pulses by 60, so at pin 10 of D1 pulses with a repetition rate of one minute are obtained.
Pulses with a frequency of 1 Hz are also supplied to the transistor switch VT1, in the collector circuit of which an LED is turned on, blinking during the operation of the timer with a period of one second.
Minute pulses with pin. 10 D1 are fed to a two-digit decimal counter on two identical chips D2 and D3. The time is set using switches S1 and S2, with S1 setting the units of minutes, and S2 - tens. For example, if you need a time of 63 minutes, set S1 to position “3”, and S2 to position “6”.
The sound-emitting device consists of transistor VT2, miniature speaker B1 and logic element “3rd” on resistor R6 and diodes VD2-VD4. While the installed counter outputs have logical zeros (or one of them has a zero), at least one of the diodes VD2 and VD4 receives a logical zero through switch S1 or S2. In this case, the diode is open and zero is also set at the connection point between R6 and R7. As soon as the set time expires, both diodes receive ones and they close. As a result, a high level voltage is supplied to the VT2 base through R6-R7.
And in order to receive a tone signal, this voltage is interrupted at a frequency of 1024 Hz using a diode VD3, the cathode of which receives this frequency from pin 11 D1. The timer is set to zero at the moment the power is turned on using capacitor C5, the charging current of which sets all four counters to zero states.
Structurally, the timer is made in a small plastic box for various small items; the handles of two biscuit switches are located on the lid and circular scales of tens and units of minutes are drawn. The speaker is also attached to this cover. Switch SB1 toggle switch. The timer is powered by two 4.5 V flat batteries connected in series.
It is possible to install a standard connector and power the timer from a 9 V network adapter for portable audio equipment. During the setup process, you may have to select the ratio of resistors R7 and R8 in such a way that the speaker does not sound until the set time has elapsed.
Any electrodynamic or electromagnetic low-power sound emitter is suitable as a speaker, for example, an electromagnetic capsule from a telephone, a speaker from a radio, etc. Chips K176IE8 can be replaced with K561IE8. Transistors KT315 - any corresponding power and structure. KD521 diodes are any low-power pulse or rectifier, and even better if they are germanium type D9. The LED is also of any visible spectrum.
Kitchen timer circuit board view
This is another craft made from trash - a timer for the kitchen, although not necessarily for the kitchen. We used parts that were lying around idle, in particular old ALS indicators, resistors soldered from old boards, etc. The basis of the device is the PIC16F628A microcontroller, one of the most common and cheapest. The timer is controlled using a valcoder and one button. Time delay range from 1 to 99 minutes. At the end of the timing cycle, an intermittent sound signal is given. There are two firmwares in the archive, the first is just a timer, and the second with some bells and whistles, more on that below.
There is also an option for indicators with a common anode. Please note that the firmware for each of the schemes is different. All differences are highlighted in red on the diagram.
After turning on the power, the set time is displayed on the indicators, the LED does not light up. By rotating the rotary dial you can change the time setting from 1 to 99 minutes. When the time is set, press the button - a short beep sounds and the timer starts counting down, the LED flashes, and the time on the indicator decreases every minute. When the time has reached zero, the timer emits intermittent sound signals and the LED lights up continuously. Now, by pressing the button, the sound signal is removed and the device returns to its original state - time setting mode. This is how the first version of the firmware works.
The second version of the firmware works the same as the first, but has several additions. In the time setting mode, if the encoder is not touched for several seconds, an animated screensaver starts running on the display. Pressing the button or rotating the encoder will turn off the animation and return to the time setting mode. During the countdown, if one minute remains, the display shows seconds from 60 to 00. When the sound signal is triggered, it will not sound indefinitely, but for about 20 seconds. Next, the display begins to display an animated screensaver (different from the one in installation mode). And also, after every minute it will remind you with a short sound signal. By pressing the button, just like in the first firmware, the timer will be reset to time setting mode. When there are 3 seconds left before the timer goes off, the timer emits a short beep for every second, i.e. 3...2...1 and further works as usual. Both firmware are available and are in the archive along with a drawing of the printed circuit board.
The sound signal is implemented using hardware PWM built into the microcontroller. The dynamic head should have a resistance of about 50 ohms. You can also use low-impedance dynamic heads (4 or 8 ohms), but in this case it is better to install a small-sized output transformer, because a large current will flow through the 4 ohm head, which can overload the power supply and trigger a reset of the microcontroller.
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Li-ion battery discharge controller
This mini device is necessary to protect li-ion batteries from deep discharge. The circuit automatically turns off the battery when the voltage drops below 2.9V. Very low current consumption - only 500 nA. The maximum consumer current is 2A. Reliably protects your battery from overdischarge. The board size is only 10x6 mm.
Homemade drilling machine
We make a homemade drilling machine from simple spare parts from a hardware store. A very necessary thing for making circuit boards. The speed and accuracy of work increases significantly.
Smart indicator
We will make our own indicator, of any shape, from SMD LEDs. Compact - minimum size 20x20 mm with a thickness of only 2 mm. Low power consumption - 1-10 mA in operation, 5 µA in sleep mode. Independent control of each LED via one wire. Brightness control - more than 100 brightness levels. Up to 100 LEDs in an indicator, with any location on the board. Possible designs - two scales of 8 LEDs and 4 service LEDs; indication of cardinal directions - 8 LEDs in a circle and 4 service ones; clock - 12 LEDs in a circle; matrix 8x8 LEDs.
Dwelcome to a fascinating worldmicroelectronics!
The first issue of the radio magazine was published in 1924. Even then, there was interest in the manufacture of radio-electronic devices at home. Using a soldering iron, wires, and later on PCB, it was possible to make a full-fledged complex device. It was very difficult, only a few understood in this area.
Now almost every schoolchild can independently make excellent quality printed circuit boards at home. Assemble a modern device on them, the functions of which are not inferior to those sold on the market. All this became possible thanks to the advent of computers and the development of the Internet. Almost every device these days is made using . They allow you to breathe life into a device, solve complex problems using programming, and receive and display various data.
Can this be done using microcontrollers? How to do it? How to develop? How to draw up a diagram correctly? How
My son's grandmother will have a birthday soon. Since I became interested in microcontrollers, I came up with the idea of giving him some kind of device, naturally, on a microcontroller and made with my own hands. Like all grandmothers, our grandmother is not an advanced user of any devices, and in principle she does not have anything special in terms of electronics. So, you can make any, not very complicated device.When we come to visit her, we are always greeted by a rich table with a large number of dishes. Therefore, we immediately decided to make a device useful in the kitchen. Together we often play various board games - lotto, various dice games. This means that our device should help here too.
After thinking a little, the son decided to do advanced kitchen timer. I helped him a little with the scheme. The main functions of our gift:
- Timer mode up to 3 hours
- Stopwatch mode
- Loud signal
- Compact size
- “Eternal” batteries - rechargeable batteries, charging like a phone, via micro usb
- And of course games - dice (random number from 1 to 6), lotto, bomb (very fun game)
Selecting components
As an indicator, we chose a three-digit LED indicator with a common anode - it has only 11 pins, which is very convenient. It’s not difficult to buy, and in principle, it’s quite economical in energy consumption (but of course not LCD).The microcontroller is STM8S003F3P6 - we have already worked with it, so everything is familiar. ST-link is already there.
The charging microcircuit and all the wiring of the MK are like a bicycle computer.
As a tweeter, very compact and loud tweeter HC0903A
Battery - LIR2032. Only 45 mAh, but this is enough for 40 hours of continuous operation of the timer. We decided to abandon the quartz resonator (pins are needed), we don’t need special accuracy, and the STM8 has a fairly accurate internal oscillator. Charge chip - TP4056.
Control - 2 tact buttons. The device is in sleep mode all the time, consumption is less than 5 µA, it can sleep for a long time. They did not make a protection board for the battery; it is not particularly necessary. MK has a lower limit of 3V, so it won’t sag much. When you turn it on, music plays, the indicator turns on (inrush current), and if the battery is dead, the MK will reboot and go into sleep mode, which is a signal to charge. It charges with a current of 100 mA in about 40 minutes, which is, in principle, very fast. The circuit and program can be downloaded on github, link at the end.
My son decided to make the case himself from a 40 x 16 mm mounting box. I painted it with acrylic paints and cut out a piece from a DVD as glass. It turned out very nice.
My son did the board routing himself in Kicad. It was he who came up with the arrangement of the components. There are buttons on the sides of the indicator, a tweeter at the bottom, and a battery on it. Everything fits tightly, nothing is loose. The board is double-sided. Made from single-sided fiberglass 0.8mm thick using the cold toner transfer method. The two halves of the board were connected and secured with jumpers. Connectors include micro usb, power supply and programming.
Program
This indicator has a common anode, so only one discharge can be output at one time. To display three digits simultaneously, a dynamic indication is required.This is done very simply programmatically. The timer is activated, and at regular intervals, with a high frequency, for example, every 300 μs, we will output one digit in a circle - 1-2-3-1-2-3. It will show us that the numbers glow at the same time, like in a movie. If you additionally add empty bits, you can control the brightness. That is, there will be such an information output scheme - 1-2-3-empty-empty-empty-empty-1-2-3-empty-empty... Brightness control is needed in order to reduce power consumption. Thus, for example, without using brightness, one discharge consumes 24 mA, but with application it can be reduced to 1-2 mA. At the same time, the numbers are still clearly and far visible. My son played with the frequency and brightness, and when everything stopped flickering, he liked it. It turned out that programming this type of indicator is quite easy and convenient.
The second difficult point is to come up with a simple, as they say, intuitive interface, when we have 3 indicator digits and 2 buttons. But I think he succeeded.
We came up with buttons like this:
- Right button - long press, change modes, there are three of them - Timer, Stopwatch, Games
- Right button - single press, change submode. For the timer - this is a choice of preset times, for the stopwatch - the choice of a regular stopwatch and with confirmation, for the game - accordingly. Various games
- Left button - single press - start/stop or move in the game, long press - setup mode, programming
- When a timer is selected, a certain number from the preset settings is immediately displayed (For example, 5,15,30 minutes), they can be reprogrammed, they are stored in ROM
- When the stopwatch is selected, it is 000
- When the games are L - lotto, 6 - bomb, C - cube.
- The numbers are displayed on the indicator in a clever way, since there are only three digits, we display the maximum number of significant elements. For example, the timer is 200 minutes 30 seconds, then we display 200. If the timer is 10 minutes 15 seconds, then we display 10.1, if it is 1 minute 25 seconds, then 1.25. At the same time, to understand that the timer or stopwatch is running, the dot blinks in time with the seconds.
- When the stopwatch is stopped, for example at 10 minutes 25 seconds, then we show alternately 10. and .25, once a second, to see the seconds too.
Tests
The first tests took place at school. Instead of a cube, fortune telling using grades. The whole class was guessing. Then the bomb is a super game. The device guesses a random time from 5 to 20 seconds and starts ticking every second. You pass it around. When the timer reaches zero - an explosion signal. The one who has the device in his hands loses.The first tests of the stopwatch and timer went well. We measured different times, checked them with an accurate clock, the error was 1-2 seconds per hour. We practiced the sound of the signal.
Presentation of a gift
The birthday has arrived. Grandma quickly completed the training and was very happy. Everyone experienced Lotto together, which was fully automated. Every 5 seconds the device beeps and produces a new number from those remaining in the bag. Everyone plays, drives the device! Those who didn't have time were late.Results
So, the device turned out just great. The practice of programming is very interesting. If you are also interested in microcontrollers, then you can make one for yourself (or as a gift) and program it. You will definitely learn:- make boards
- solder smd components
- program STM8
- work with batteries
- handle buttons
- make different sounds
- work with timers and process temporary events
- fight energy consumption