AVT 1995 User manual

Timer designed for precise countdown of preset time

intervals in the range of 1 second...99 minutes. It

enables entering the countdown time in minutes and

seconds. Its resolution in the range from 1 second to

9 minutes and 59 seconds is 1 second, while in the

range of 10.99 minutes it increases to 10 seconds. The

integrated relay and easy, intuitive operation qualify

the unit for the implementation of timing functions in

uncomplicated automation systems.

• executive circuit - relay 230 VAC / 8 A

• supply: 8...12 VDC / 80 mA

Specifications

• relay connector NO or NC (normally open or

• settings memory

• maximum timer range - 99 minutes

normally closed)

• board sizes: 58×48 mm and 53×27 mm

Figure 1 shows schematic diagram of the timer. The

device is designed to be supplied with 8-12VDC.

Rectifier diode D1 protects the circuit from incorrect

polarity. Supply voltage is stabilised by U1, while

capacitors C1... C4 ensure that it is adequately filtered.

The operation of the timer is controlled by an

ATtiny26 microcontroller timed by an internal clock

signal. Its operating status is reflected on a triple

seven-segment display with a common anode.

Cathodes of the 3-digit multiplexed LED display are

connected via current-limiting resistors R5.R12 to the

PA0-PA7 ports of the microcontroller. Function of the

keys that switch on the power supply to the displays

is performed by transistors T1-T3 controlled from

ports PB2-PB4. For settings and timer control, the unit

is equipped with 3 buttons marked S1, S2 and S3.

Signals from the buttons are routed to ports PB0 and

PB1 and PB6, the active level is logical '0'. A relay of

type RM84P12 (coil 12 VDC, contacts 8 A/230 VAC) is

used as the executive circuit. To extend the timer's

functionality, the NC and NO contacts are provided

for the relay.

Circuit description

Precise Timer 1 second...99 minutes

AVT 1995

ASSEMBLY DIFFICULTY

kits

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Figure 1. Schematic diagram

Fig. 2. Components arrangement on PCB

If the circuit is mounted without any errors, using a

preprogrammed microcontroller and with efficient

components, it will work as soon as it is energized.

When controlling a load of significant power,

attention must be paid to the load on the relay

contacts and PCB tracks. To improve their load

capacity, the exposed tracks can be additionally

tinned or, even better, a copper wire can be laid over

them and soldered.

Mounting of the circuit is typical and should not

cause any problems; it follows a standard procedure,

starting with the smallest components and ending

with the largest. Once the two boards have been

mounted, connect them together using an angled

goldpin strip.

The timer must be mounted on two PCBs, the design

of which is shown in Figure 2.

Mounting and start-up

A blinking dot next to the unit digit indicates that the

timer is running.

Operation of the timer is simple and intuitive. The S1

and S2 buttons are used to increase and decrease

values, while the S3 button is used to start

countdown. Each time S2 is pressed, the value will

increase and each time S1 is pressed, the value will

decrease. To change the value faster without having

to press the button repeatedly, press and hold the

respective button. On the three-digit display, in the

range of 1 second from 9 minutes and 59 seconds,

the setting resolution is 1 second, while above this

range it increases to 10 seconds. The set value is

remembered in non-volatile memory, so you do not

need to re-enter it when the device is restarted.

Once the countdown has started, you can stop the

timer at any time by pressing the S3 button. In this

mode, the digits on the display will start blinking.

Pressing the S3 button again briefly resumes the

countdown, while holding the S3 button longer

returns the device to its initial value. When using the

timer, you should be aware that the timer may be

subject to a certain degree of inaccuracy, particularly

in the minutes range.

Operation

R6-R13:...................100 Ω (brown-black-brown-gold)

Capacitors:

C1, C2:.....................100 μF !

Semiconductors:

Resistors:

R1-R5: .....................10 kΩ (brown-black-orange-gold)

C3-C5: .....................100 μF (can be labelled 104)

D1, D2:....................1N4007 !

SV1:..........................goldpin 1×16pin

U1:............................78L05 !

Other:

S1-S3:......................microswitch button

U2:............................ATtiny261 + base

T4: ............................BC547 (BC548) !

LED1: .......................display AD5636

ZAS, NO, NC: ........screw terminals

PK1:..........................relay RM84P12 (or similar)

T1-T3:......................BC557 (BC558) !

List of elements

Begin assembly by soldering the components onto the board in order of size from smallest to largest.

When mounting components marked with an exclamation mark, pay attention to their polarity.

Access the high-resolution images using links and download the PDF.

Frames with diagrams of the leads and symbols of these components on the PCB and photographs of the

assembled kit may be helpful.

Pobierz PDF

1 sek - 99 min

Figure 3. Relay switched on during countdown

Figure 4. Relay switched off during countdown

START

The self-assembly kits are intended for educational and demonstration purposes only. They are not intended for use in commercial applications. If they are used in such applications, the

purchaser assumes all responsibility for ensuring compliance with all regulations

AVT SPV reserves the right to make changes without prior notice.Installation and connection of the appliance not in accordance with the instructions, unauthorised modification of

components and any structural alterations may cause damage to the appliance and endanger persons using it. In such a case, the manufacturer and its authorised representatives shall

not be liable for any damage arising directly or indirectly from the use or malfunction of the product.

This symbol means do not dispose of your

product with your other household waste.

Instead, you should protect human health

and the environment by handing over your

waste equipment to a designated collection

point for the recycling of waste electrical

and electronic equipment.

Leszczynowa 11 Street,

03-197 Warsaw, Poland

https://sklep.avt.pl/

AVT SPV Sp. z o.o.