Hi
I'm a novice to electronics and I need some help.

I'm planning on building a simple time delay system, using several box units (see illustrations) with a singe cable running from box to box, and a built in 0,1 second delay between each box.

Specs / operations:

• The system must be versatile in the sense that several boxes can be added to the chain, from 2 to 30 boxes.
• Box 1 has an outlet for an external on/off switch and a power supply (a 12v car or MC-battery.)
• As long as the on/off switch is on the current flows through the whole chain with a 0,1 sec delay between each box.

I understand the IC555 / NE555 timer circuit (along with a few other electronic parts) is the best to use for this project. What other parts do I need?
I would be grateful for a complete and detailed hook-up.

 

Welcome to AAC.

If all you want to do is trigger a series of relays, a simple RC (resistor and capacitor) delay on the gate of a mosfet (e.g., 2N7000 or 2N7002(logic level)) in series with the relay's coil to ground (i.e., power to relay coil, coil to drain of mosfet and source of mosfet to ground) should suffice. No 555's required.

 

Welcome to AAC.

If all you want to do is trigger a series of relays, a simple RC (resistor and capacitor) delay on the gate of a mosfet (e.g., 2N7000 or 2N7002(logic level)) in series with the relay's coil to ground (i.e., power to relay coil, coil to drain of mosfet and source of mosfet to ground) should suffice. No 555's required.

Please keep in mind that I'm still a novice and not 100% sure what you mean
Each delay/box must be triggered consecutive after one another as long as the power is on. I would be extremely grateful for a complete and detailed hook-up.

 

How accurate does the 0.1 second need to be?
How often does the system cycle?
Can more than one pulse propagate at once?



Details are everything.

 

Post deleted.

 

How accurate does the 0.1 second need to be?
How often does the system cycle?
Can more than one pulse propagate at once?

Details are everything.

The 0,1 second delay has to be accurate.
The system cycles as long as the power stays on.
No, only one pulse.

 

The 0,1 second delay has to be accurate.
The system cycles as long as the power stays on.
No, only one pulse.

Can you put some numbers to it? "Accurate" is kind of a boundless term.

A percentage, or a +- this much kind of answer.

 

Can you put some numbers to it? "Accurate" is kind of a boundless term.

A percentage, or a +- this much kind of answer.

Sorry +/- 5% perhaps..

 

The system cycles as long as the power stays on

Do you mean that once the last box gets its power (after N delays) the whole sequence starts again?

 

Do you mean that once the last box gets its power (after N delays) the whole sequence starts again?

No, it cycles to the end (after N delays), once.

 

I would be extremely grateful for a complete and detailed hook-up.

I think this is what jpanhalt intended (post #2) :-

 

Following up on @jpanhalt’s post, a simple RC network input to a CMOS Schmitt trigger, such as a 40106, can be used to create a time delay. The circuit is simple.

Lady Ada’s site has a calculator which determines the delay for a given set of components. (http://www.ladyada.net/library/rccalc.html)

I played around with various values and got a delay of .1+-5%. I’ve included screen shots below. I couldn’t get exactly .1 second with standard values. However, there is a site that has a calculator for non-standard specific resistor values by paralleling standard resistor values. I don’t remember the site, but someone else here may.

Temperature changes may affect the delay, so either detailed analysis or experimentation can minimize this effect.

 

Post #11 seems right on the money conceptually.

it requires individual adjustment for time calibration.
The timing would also be sensitive to power supply voltage variations.

If the timing needs to be tight and fixed, then you would need a more precision timing circuit that had a reference voltage- to set the trigger point and charging current of the timing capacitor.

 

Is it okay if you have to tweak a potentiometer to adjust each box delay to be within the desired accuracy?