# Delay on - Instant off timer

Thread Starter

#### theotyflos

Joined Apr 29, 2018
9
Hi to all - newbie here,

I am a programmer with basic knowledge of electonics, so please forgive my ignorance.
I'm trying to create a circuit (maybe using a 555???) that meets the following criteria:

The circuit has 2 inputs, the 1st is a NC momentary switch and the 2nd one is a NO momentary switch, and one output normally in low state.

When 1st input switches to open state, the circuit should wait for a few seconds (5 to 10 is ok - I don't care for the exact time)
and then it should trigger the output to high state and KEEP IT HIGH (even if 1st input returns to closed state) UNTIL the second switch is pressed.
When 2nd switch is pressed, the output must return to low state and the circuit must be IMMEDIATELLY (in a few milliseconds) ready for the next cycle.

I'm searching the internet for three days now to no avail. I've tried dozens of schematics but none seems to meet the above requirements.

I can create the circuit using an arduino board, but i would like to use more basic components.

If anyone can help I would appeciate it.

TIA.

PS. Forgot to mention that I don't care if it is TTL or CMOS or whatever, power voltage can be from 5 to 24 volts.

#### -live wire-

Joined Dec 22, 2017
912
I think you want a latch that gets reset (turned off) by the second button. When the first is high, even if it's for just a moment, the latch stays high. Then when it's high it should charge up a a capacitor through a resistor. The charging should take the desired delay time. That goes into a comparator. When the cap gets above a certain voltage, it pulls a comparator high. Then if the latch is pulled low, it pulls a transistor (MOSFET or BJT) high that quickly discharges the capacitor.

Thread Starter

#### theotyflos

Joined Apr 29, 2018
9
Hi -live wire-

thanks for replying,

That's exactly what I want ... I think; the problem is ... I don't have the knowledge to implement the circuit.

#### jpanhalt

Joined Jan 18, 2008
10,522
That sounds like a job for an interrupt.

#### cmartinez

Joined Jan 17, 2007
7,174
Hi to all - newbie here,

I am a programmer with basic knowledge of electonics, so please forgive my ignorance.
I'm trying to create a circuit (maybe using a 555???) that meets the following criteria:

The circuit has 2 inputs, the 1st is a NC momentary switch and the 2nd one is a NO momentary switch, and one output normally in low state.

When 1st input switches to open state, the circuit should wait for a few seconds (5 to 10 is ok - I don't care for the exact time)
and then it should trigger the output to high state and KEEP IT HIGH (even if 1st input returns to closed state) UNTIL the second switch is pressed.
When 2nd switch is pressed, the output must return to low state and the circuit must be IMMEDIATELLY (in a few milliseconds) ready for the next cycle.

I'm searching the internet for three days now to no avail. I've tried dozens of schematics but none seems to meet the above requirements.

I can create the circuit using an arduino board, but i would like to use more basic components.

If anyone can help I would appeciate it.

TIA.

PS. Forgot to mention that I don't care if it is TTL or CMOS or whatever, power voltage can be from 5 to 24 volts.
Two 555's connected in tandem should do the trick ... are you familiar with LTSpice?

Thread Starter

#### theotyflos

Joined Apr 29, 2018
9
Hi jpanhalt,

That sounds like a job for an interrupt.
I can create the circuit using an arduino board, but i would like to use more basic components.
thanks for replying anyway.

Thread Starter

#### theotyflos

Joined Apr 29, 2018
9

#### ScottWang

Joined Aug 23, 2012
6,963
Is this a homework or just a personal practice?

#### cmartinez

Joined Jan 17, 2007
7,174
No, I only use KiCad occasionally and http://www.falstad.com/circuit/ for simulations.
LTSpice is far better than falstad, and it's downloadable and installable in your computer ... and it's got the perfect price: $0.00 usd, or whatever currency you wish to use Anyway, I strongly suggest you download it, and start playing with the 555 examples ... it's very much worth it if you want to start learning the basic stuff. Thread Starter #### theotyflos Joined Apr 29, 2018 9 Is this a homework or just a personal practice? Personal practice. Thread Starter #### theotyflos Joined Apr 29, 2018 9 LTSpice is far better than falstad, and it's downloadable and installable in your computer ... and it's got the perfect price:$0.00 usd, or whatever currency you wish to use

Anyway, I strongly suggest you download it, and start playing with the 555 examples ... it's very much worth it if you want to start learning the basic stuff.
I only have a Linux box. I haven't use windows for many years now... Do you know if LTSpice works under Wine?

#### Dodgydave

Joined Jun 22, 2012
9,685
Hi to all - newbie here,

I am a programmer with basic knowledge of electonics, so please forgive my ignorance.
I'm trying to create a circuit (maybe using a 555???) that meets the following criteria:

The circuit has 2 inputs, the 1st is a NC momentary switch and the 2nd one is a NO momentary switch, and one output normally in low state.

When 1st input switches to open state, the circuit should wait for a few seconds (5 to 10 is ok - I don't care for the exact time)
and then it should trigger the output to high state and KEEP IT HIGH (even if 1st input returns to closed state) UNTIL the second switch is pressed.
When 2nd switch is pressed, the output must return to low state and the circuit must be IMMEDIATELLY (in a few milliseconds) ready for the next cycle.

I'm searching the internet for three days now to no avail. I've tried dozens of schematics but none seems to meet the above requirements.

I can create the circuit using an arduino board, but i would like to use more basic components.

If anyone can help I would appeciate it.

TIA.

PS. Forgot to mention that I don't care if it is TTL or CMOS or whatever, power voltage can be from 5 to 24 volts.
Draw a block diagram of what you want to happen...

Sounds like a CD4013, with a capacitor on the clock pin.

#### jpanhalt

Joined Jan 18, 2008
10,522
Hi to all - newbie here,
I am a programmer with basic knowledge of electonics, so please forgive my ignorance.
I'm trying to create a circuit (maybe using a 555???) that meets the following criteria:
Hi jpanhalt,
thanks for replying anyway.
Why use a 555 when a 10F3xx or 12F6xx will do the job with fewer components?

#### cmartinez

Joined Jan 17, 2007
7,174
Why use a 555 when a 10F3xx or 12F6xx will do the job with fewer components?
I agree ... but the TS stated

i would like to use more basic components.
On the other hand, the use of an MCU would require a programmer.

@theotyflos, it's up to you. Which way would you like to go? The really basic way (more components, a bit more complicated in hardware terms) or an MCU, which is far less components, and requires some programming (and a device programmer).

I could help you with the 8051 architecture, but I'm not familiar with PIC's, which is what I think jpanhalt is suggesting.

#### MaxHeadRoom

Joined Jul 18, 2013
21,635
Some of the small 12F versions can be set for a internal 29Khz clock so easily run as 1 sec clock and simulate many of the 555 functions or 556.
Max.

Thread Starter

#### theotyflos

Joined Apr 29, 2018
9
Why use a 555 when a 10F3xx or 12F6xx will do the job with fewer components?
For Learning.

#### cmartinez

Joined Jan 17, 2007
7,174
For Learning.
Then go for it. Download LTSpice, and we'll help you anyway we can

#### bertus

Joined Apr 5, 2008
20,888
Hello,

LTspice will run fine with wine on linux.

Bertus

Thread Starter

#### theotyflos

Joined Apr 29, 2018
9
Which way would you like to go?
I would like to use "basic" elctronic components. I think that's the only way if you want to understand electronics.

MCU, which is far less components, and requires some programming
I am a programmer and I can easily create the circuit using PICs or ARMs. I just want to learn more about electronics since my knowledge to the subject is very basic.

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#### jpanhalt

Joined Jan 18, 2008
10,522
For Learning.
Well then, show us what you ave done so we can help. Giving you a circuit with a 555 will only help you learn how to solder, which you already know how to do.

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