Project Advice need - Newbie

Thread Starter

RigidCollision

Joined Dec 10, 2018
8
Hi Everyone,
I am looking for some general pointers and advice for a project I would like to create.

I have designed (and had manufactured) a PCB backbone for an Ardiuno project, have a basic knowledge of electronics and good soldering skills.

I have an old vehicle which relies on a toggle switch for indicators. I would like to improve this (as the indicators often get left on).
My thought would be to replace the 3 way toggle (OFF-On-OFF) with a 2 way momentary switch MOMENTARY ON-OFF- MOMENTARY ON.
I would need to feed the indicator circuit for 5 second and then switch off. However, If the brakes were applied the counter would continually be reset to zero until the brakes were released then continue the count as normal.

This allows lane changing but holds the indicator on if turning across the oncoming traffic or waiting at a junction.

I would utilise the 12v being used by the indicator switch along with its outputs to the indicators along with another input from the brake light feed to reset the counter.

Where would a novice start with this? I am happy to 'play' with a bread board design and work up to a robust PCB solution for the final design.

Any guidance, even just to point me in the right direction would be greatly appreciated.

Kind regards
 

MrChips

Joined Oct 2, 2009
22,089
Welcome to AAC!

In a situation like this you want to respond to a change in the signal, not the level of the signal.
There are two simple ways to implement this.
1) You can use what is known as a monostable circuit which produces a short pulse when a change is detected. You can configure the monostable to produce a pulse either on the rising transition, falling transition, or both. You can also select the width of the pulse.

2) A simple capacitor-resistor circuit can create a crude implementation of the above. The details will depend on the rest of the circuit requirements such as the desired current and voltage output.
 

danadak

Joined Mar 10, 2018
4,057
Being addicted to processors I would tackle it with a processor that -

1) Has count/timer capabilities and fairly accurate, a couple of %
2) Debounce facilities for mechanical switch closures
3) Ability to not generate false triggers on power up
4) Onboard features for "other" functional additions at a later time,
like analog, display, COM...
5) Minimum amount of coding, possibly none
6) Basic configurable logic
7) OnChip routing of signals and logic, GUI drag/drop/configure tool
8) Simple low cost dev board to use and interface to

Are you starting with processors ?

Regards, Dana.
 
Last edited:

#12

Joined Nov 30, 2010
18,210
This looks like a move to, "Embedded Systems and Microcontrollers" if TS wants to continue the conversation. Just an idea. MrChips has the authority to make that decision.
 

Thread Starter

RigidCollision

Joined Dec 10, 2018
8
Welcome to AAC!

In a situation like this you want to respond to a change in the signal, not the level of the signal.
There are two simple ways to implement this.
1) You can use what is known as a monostable circuit which produces a short pulse when a change is detected. You can configure the monostable to produce a pulse either on the rising transition, falling transition, or both. You can also select the width of the pulse.

2) A simple capacitor-resistor circuit can create a crude implementation of the above. The details will depend on the rest of the circuit requirements such as the desired current and voltage output.
Hi, Thanks for the advice. I guess we are talking about a 555 timer circuit?
I have placed a fresh post in the Projects Forum.
https://forum.allaboutcircuits.com/...uit-design-help-for-555-timer-project.155099/
 
Last edited:

MrChips

Joined Oct 2, 2009
22,089
555-timer is one way to produce a pulse from a negative-going pulse applied to the trigger input. This trigger pulse must be shorter in duration than the 555 output pulse.

There are other circuits such as 74xx121, 74xx123, 14528, 14538 which are called monostable multivibrators.
With these, you can select rising or falling transitions and the trigger pulse duration can be any length.

You do have to consider another characteristic:

non-retriggerable - The output pulse has a fixed duration regardless of the repetition rate of the trigger signal.
retriggerable - The output pulse duration will be extended as long as there is a trigger pulse appearing before the output times out.
 
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