Micro Subway

All purpose timer MST1000

The single chip all-purpose timer MST1000 is a very low cost easy to use single chip solution brought to you by Micro Subway electronics. We do all the work for you, simply plug the battery, setup the chip and press the button; your application is put into action after the preset period of time is elapsed and is then automatically reset. It can’t be easier than that!

The MST1000 timer connects to normally open (NO) push button switches (SW – N. O.) and LED with the color of your choice as follows:

Figure 1. MST1000 typical application circuit.

Here is a list of the recommended part values:

Part	Value	Note
R1	4.7 K	Resistor
R2	4.7 K	Resistor
R3	4.7 K	Resistor
RL	220 Ohms	Resistor – LED current limit resistor
RO	4.7 K	Resistor – Output pull-up resistor
Switch A	Normally open switch	Push button
Switch L	Normally open switch	Push button
Switch H	Normally open switch	Push button
C	0.1 uF	Ceramic disk
C1	22 pF	Ceramic disk
C2	22 pF	Ceramic disk
XTL	4 MHz	Crystal
U1	MST1000	Micro Subway timer chip
LED	5 mm LED	Any: RL = (5 – V forward) / 0.01

۩ Theory Of Operation ۩

The MST1000 is an agile component that is used to generate useful timing and delay signals. For instance, you may need to activate a system after a push button is depressed, turn OFF lights automatically after certain period from turning them ON, extend operation of any device that operates on narrow pulse width, and so on. The application of this versatile chip are only limited by the imagination. Here is a list of possible applications that the MST1000 can serve its purpose:

Delay timer.
Pulse extender.
Digital Echo generator.
Delayed response generator.
Energy saving electronic switch.
Security system entry/exit delay generator.
Event sequencing for device multiple operations.
Dead Bolt / Strike electrical – electronic lock systems.

Switch A operation:

Switch A is mainly used to initiate the timing / delay cycle. It is connected to the chip (pin A), which is pulled high via a 4.7 K resistor. Once switch A is depressed the output at pin O of the chip goes low for a period of time equals to L then goes high for a period of H then goes back to low level. It is the period of time which the output O remains high that activate or initiate the desired response or device.

Figure 2. Depressing switch A activates the cycle components L and H periods.

Both of (L)ow and (H)igh periods can be easily programmed via switches H and L as depicted in the circuit of figure 1 above.

Switches L and H operation:

Depressing switches L or H can easily reprogram the periods L or H accordingly. Every time you depress the switch you advance to the next period. For example if the present L period is 10 seconds and you depress switch L you advance period L from 10 seconds to 15 seconds. On power on both L and H are reset to 1 second each. Here are the available time settings for each L and H periods:

Switch L or H Depression #	L or H In Seconds	Note L is Low and H is High	Sequence #
Power ON	LED blinks twice indicating start of sequence
Default	0	Output O follows switch A	1
1	1	Output O stays High or Low for 1 second	2
2	2	Output O stays High or Low for 2 seconds	3
3	5	Output O stays High or Low for 5 seconds	4
4	10	Output O stays High or Low for 10 seconds	5
5	15	Output O stays High or Low for 15 seconds	6
6	20	Output O stays High or Low for 20 seconds	7
7	25	Output O stays High or Low for 25 seconds	8
8	30	Output O stays High or Low for 30 seconds	9
9	35	Output O stays High or Low for 35 seconds	10
10	40	Output O stays High or Low for 40 seconds	11
11	45	Output O stays High or Low for 45 seconds	12
12	50	Output O stays High or Low for 50 seconds	13
13	55	Output O stays High or Low for 55 seconds	14
14	60	Output O stays High or Low for 60 seconds	15
15	120	Output O stays High or Low for 120 seconds	16
16	LED flashes twice – return to sequence # 1

Table 1. Setting L and H times via switches L and H. Delays as function of switch depression sequence. Note that the LED blinks once while progressing from sequence 1 to 16. LED blinks twice on power up or after jumping from sequence 16 to 1.

Putting things together:

Example 1: The light needs to turn ON after 30 seconds for 5 seconds only – after depressing switch A. To do that, turn ON the power to the MST1000 chip by applying the 5 volts DC to pin VCC as per figure 1 above. The LED will blink twice indicating the initiation of sequence #1 after power ON. Depress switch L 8 times then depress switch H 3 times. Every time you depress L or H switch the LED blinks once indicating succession to the next sequence. To initiate the intended cycle just depress switch A. The light connected to the output pin O will remain OFF for 30 seconds, then turn ON for 5 second, then turn OFF. To repeat the last cycle only just depress switch A again and you are set.

Example 2: The motor needs to turn ON for 20 seconds only after initiating the cycle – or depressing switch A. To do that, turn ON the MST1000 chip, the LED will blink twice indicating power ON and initiation of sequence 1. If you depress switch A the motor will turn ON, once you remove your finger the motor stops. Depress switch H 6 times, the H period is now set to 20 seconds. Every time you depress H or L switches the LED blinks once indicating the succession to the next sequence. To initiate the intended cycle just depress switch A. The motor will immediately move and will stop after 20 seconds.

Driving power loads:

At a times you may need to drive loads that operate off higher voltages and currents than the MST1000 chip power can provide at the output pin O. To do this use a transistor driver circuit to accomplish this task. All what you need to do is connect the output pin O of the MST1000 chip to the “Input to control relay” point of the circuit below.

Figure 3. Connecting the MST1000 output to the high power transistor load driver.

Points X and Y of the RLY1 relay connect to the points of the high voltage high current device to control, such as the AC operated lights or motors. Different transistors can be used, refer to the transistor data sheet for maximum power rating. If you exceed the maximum power rating of the transistor you are using you may cause damage to the circuit or your equipment. Remember to isolate the 5 VDC from the 9 VDC if using two different supplies. All grounds may connect together. Please contact us should you need any further support.

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