This is a straightforward maths question, for solving an electronic problem.

The time delay of a timer is given as 1.1*R*C where the time is in seconds, resistance R in ohms and capacitance C in farads. eg. a 100 kOhm resistor with a 10 microFarad capacitor gives a time delay of 1.1 seconds.

I want to get a time delay between 3.95 and 4 seconds.

I have 6 capacitors with sizes (in microFarads) 4.7, 10, 22, 33, 47, 100

Resistors (in kOhms) come in sizes 39, 47, 56, 68, 82, 100,120, 150, 180, 220, 270, 330, 390, 470, 560, 750, 1000

How many of the 6 capacitors can be used to get that time delay with one resistor?
For each of the 6 capacitors what pair of resistors in parallel (if possible) will give the correct time delay?

eg. the resistance of a 100 & 150 kOhm resistor in parallel is 1/(1/100+1/150) = 60 kOhm.

———————

Note, this is a practical problem, I need to get 5 time delays in that range.

generally with higher value C and R the leakage of the capacitors becomes an R component you don’t want (and changes with temp and age), so instead you clock a smaller RC arrangement and use the steps.

>I want to get a time delay between 3.95 and 4 seconds.

Not sure what your chances are of getting +/- .025 seconds accurancy and reliable adjustment/changes with capacitors, even if the RC were stable over whatever temp range (and age and component spread etc), then there are trigger threshold variations (if you are triggering at some upper and lower voltages).

If you are hoping the plonk within that +/- .025 for single time delay you’d have to trim it, and it may wander outside that anyway.

resistors and capacitors won’t have the accuracy you need

wookiemeister said:

resistors and capacitors won’t have the accuracy you need

need something with more lamella feedback characteristics?

>I want to get a time delay between 3.95 and 4 seconds.

for this you need a chronometer.

I would use a 555 timer in conjunction with capacitors and resistors to create a timed pulse

You should use something like this…

http://www.jaycar.com.au/productView.asp?ID=ZL3555

another approach could be straight forward clockwork, the hand goes around and strikes contacts as it travels around

wookiemeister said:

another approach could be straight forward clockwork, the hand goes around and strikes contacts as it travels around

eg: the average digital is way less accurate than an analog chronometer.

wookiemeister said:

another approach could be straight forward clockwork, the hand goes around and strikes contacts as it travels around

The problem though is maintaning power, over the humps.

fsm said:

You should use something like this…

http://www.jaycar.com.au/productView.asp?ID=ZL3555

yeah the 555 timer is a good way to go for a simple way to create timed pulses

you could have the timed output of one 555 timer linked to another 555 timer, as the first timer pulses whatever it also pulses a voltage on the trigger input of another 555 timer

its a good way of creating timed pulses

if you need other stuff with that timing you’d be better off with a microcontroller

wookiemeister said:

fsm said:

You should use something like this…

http://www.jaycar.com.au/productView.asp?ID=ZL3555

yeah the 555 timer is a good way to go for a simple way to create timed pulses

you could have the timed output of one 555 timer linked to another 555 timer, as the first timer pulses whatever it also pulses a voltage on the trigger input of another 555 timer

its a good way of creating timed pulses

if you need other stuff with that timing you’d be better off with a microcontroller

ie: a chronometer.

roughbarked said:

wookiemeister said:

another approach could be straight forward clockwork, the hand goes around and strikes contacts as it travels around

The problem though is maintaning power, over the humps.

you use a geared electric motor with a reliable powersource

by varying the voltage you make the strikes slower or faster

wookiemeister said:

roughbarked said:

wookiemeister said:

another approach could be straight forward clockwork, the hand goes around and strikes contacts as it travels around

The problem though is maintaning power, over the humps.

you use a geared electric motor with a reliable powersource

by varying the voltage you make the strikes slower or faster

whusedhewasdum?

roughbarked said:

wookiemeister said:

fsm said:

You should use something like this…

http://www.jaycar.com.au/productView.asp?ID=ZL3555

yeah the 555 timer is a good way to go for a simple way to create timed pulses

you could have the timed output of one 555 timer linked to another 555 timer, as the first timer pulses whatever it also pulses a voltage on the trigger input of another 555 timer

its a good way of creating timed pulses

if you need other stuff with that timing you’d be better off with a microcontroller

ie: a chronometer.

I was being specific

any clock is a chronometer

wookiemeister said:

roughbarked said:

wookiemeister said:

yeah the 555 timer is a good way to go for a simple way to create timed pulses

you could have the timed output of one 555 timer linked to another 555 timer, as the first timer pulses whatever it also pulses a voltage on the trigger input of another 555 timer

its a good way of creating timed pulses

if you need other stuff with that timing you’d be better off with a microcontroller

ie: a chronometer.

I was being specific

well you need to be more so.
wookiemeister said:

any clock is a chronometer

no

roughbarked said:

wookiemeister said:

roughbarked said:

The problem though is maintaning power, over the humps.

you use a geared electric motor with a reliable powersource

by varying the voltage you make the strikes slower or faster

whusedhewasdum?

the IRA used clockwork time pieces in their bombs on a regular basis – in fact it was a hallmark of their devices, a clockwork time piece driven by a motor or spring with striking contacts. the times of strike could be visually confirmed rather than by calculation and prayer that electronics would do what they should.

see ya!!

Enter two of the required values and Hit the third button to calculate the required value. You may also choose the suitable units.

http://www.referencedesigner.com/rfcal/cal_05.php

HTH

<><><><><><><>

macx

wookiemeister said:

roughbarked said:

wookiemeister said:

you use a geared electric motor with a reliable powersource

by varying the voltage you make the strikes slower or faster

whusedhewasdum?

the IRA used clockwork time pieces in their bombs on a regular basis – in fact it was a hallmark of their devices, a clockwork time piece driven by a motor or spring with striking contacts. the times of strike could be visually confirmed rather than by calculation and prayer that electronics would do what they should.

Mechanics in the way of clockwork can be timed via several methods. Yes the same can be done with electronics but the methodology was learned form making clocks. This tech is thousands of years old. The thing I mentioned is, that if one takes planned obsolescence into account, then digital timers aren’t worth thinking about.

macx said:

Enter two of the required values and Hit the third button to calculate the required value. You may also choose the suitable units.

http://www.referencedesigner.com/rfcal/cal_05.php

HTH

<><><><><><><>

macx

:) hi ya. :)

As regards digital watch or clock circuits. less than 20% of those manufactured reach chronograph capability.

>>>:) hi ya. :)

and you also….

Just popping in for a while over the festive season.

I see things have not changed a great deal.

:)

macx

macx said:

>>>:) hi ya. :)

and you also….

Just popping in for a while over the festive season.

I see things have not changed a great deal.

:)

macx

indeed they have but hey.. change is the only constant?

actually just looking

http://www.miniinthebox.com/pro-mini-microcontroller-circuit-board-for-arduino-5v-16mhz_p764222.html?currency=AUD&litb_from=paid_adwords_shopping&pla_adwid=9286587055_138818343_9138179223_60166996743&gclid=CLSilfyLwLsCFcXFpAodIDoAAw

$12.18

this arduino can deliver many output signals , can be programmed easily, doesn’t need extra components

a 555 approach using separate ICs with resistors and capacitors will require more time to put together than the timers

this is why microcontrollers rule the roost

roughbarked said:

macx said:

>>>:) hi ya. :)

and you also….

Just popping in for a while over the festive season.

I see things have not changed a great deal.

:)

macx

indeed they have but hey.. change is the only constant?

if that sounded screwed.. think about it for a bit.

wookiemeister said:

actually just looking

http://www.miniinthebox.com/pro-mini-microcontroller-circuit-board-for-arduino-5v-16mhz_p764222.html?currency=AUD&litb_from=paid_adwords_shopping&pla_adwid=9286587055_138818343_9138179223_60166996743&gclid=CLSilfyLwLsCFcXFpAodIDoAAw

$12.18

this arduino can deliver many output signals , can be programmed easily, doesn’t need extra components

a 555 approach using separate ICs with resistors and capacitors will require more time to put together than the timers

this is why microcontrollers rule the roost

as long as it is accurate.. it will after that, it needs a tech to know which part to replace or poise.

“A chronometer is a high-precision watch capable of displaying the seconds and housing a movement that has been tested over several days, in different positions and at different temperatures, by an official neutral body (COSC).

Each chronometer is unique, identified by a number engraved on its movement and a certification number given by the COSC.

Each movement is individually tested for several consecutive days, in 5 positions and at 3 temperatures.

Each movement is individually measured. Any watch with the denomination “chronometer” is provided with a certified movement.”

><><><><><>

from here:

http://www.cosc.ch/chronometre.php?lang=en

macx

macx said:

“A chronometer is a high-precision watch capable of displaying the seconds and housing a movement that has been tested over several days, in different positions and at different temperatures, by an official neutral body (COSC).

Each chronometer is unique, identified by a number engraved on its movement and a certification number given by the COSC.

Each movement is individually tested for several consecutive days, in 5 positions and at 3 temperatures.

Each movement is individually measured. Any watch with the denomination “chronometer” is provided with a certified movement.”

><><><><><>

from here:

http://www.cosc.ch/chronometre.php?lang=en

macx

Blame the carpenter turned clockmaker, John Harrison for his attendance to perfection of the capacity for accuracy.

>>>…this is why microcontrollers rule the roost

The system timing will only be as good (accurate and stable) as the system “clock, usually an el cheapo’ crystal osc with little or no regard to temperature compensation and they invariably use a small equally el cheapo’ capacitor in the osc circuitry.

Digital is not a synonym for accurate!!

:)

macx

>>Blame the carpenter turned clockmaker, John Harrison for his attendance to perfection of the capacity for accuracy.

Indeed.

There is a documentary on Harrison and his clocks (and his fight with the Admiralty) which shows on TV every now and again.

I am a great admirer of Harrison.

macx

macx said:

>>>…this is why microcontrollers rule the roost

Digital is not a synonym for accurate!!

:)

macx

This is what I’ve been trying to get across.

OK so we think and generally do believe that why digital clocks overran the mechanical ones, was simply because they were more accurate.. this is erroneous. the reason was because they were cheap to make.

macx said:

>>Blame the carpenter turned clockmaker, John Harrison for his attendance to perfection of the capacity for accuracy.

Indeed.

There is a documentary on Harrison and his clocks (and his fight with the Admiralty) which shows on TV every now and again.

I am a great admirer of Harrison.

macx

Myself as well they say that Jesus was a carpenter.. then if so he would know the meaning of FN.

roughbarked said:

macx said:

>>Blame the carpenter turned clockmaker, John Harrison for his attendance to perfection of the capacity for accuracy.

Indeed.

There is a documentary on Harrison and his clocks (and his fight with the Admiralty) which shows on TV every now and again.

I am a great admirer of Harrison.

macx

Myself as well they say that Jesus was a carpenter.. then if so he would know the meaning of FN.

the revised opinion based upon substantial evidence was that the term ‘carpenter’ passed for the term ‘engineer’ before industrialisation. They believe his father was an engineer of the age……

Riff-in-Thyme said:

roughbarked said:

macx said:

>>Blame the carpenter turned clockmaker, John Harrison for his attendance to perfection of the capacity for accuracy.

Indeed.

There is a documentary on Harrison and his clocks (and his fight with the Admiralty) which shows on TV every now and again.

I am a great admirer of Harrison.

macx

Myself as well they say that Jesus was a carpenter.. then if so he would know the meaning of FN.

the revised opinion based upon substantial evidence was that the term ‘carpenter’ passed for the term ‘engineer’ before industrialisation. They believe his father was an engineer of the age……

This is all cuckoo.

turn the page to cuckoo clocks.

A Brief History of Atomic Clocks at NIST

http://tf.nist.gov/cesium/atomichistory.htm

“1999 — NIST-F1 begins operation with an uncertainty of 1.7 × 10-15, or accuracy to about one second in 20 million years, making it one of the most accurate clocks ever made (a distinction shared with similar standards in France and Germany).”

…and there are today even more accurate clocks, but they have not (yet) been adopted as “standards” because they do not have the “history” of the Caesium beam clocks. eg hydrogen maser, quantum dot technology etc.

macx

roughbarked said:

Riff-in-Thyme said:

roughbarked said:

Myself as well they say that Jesus was a carpenter.. then if so he would know the meaning of FN.

the revised opinion based upon substantial evidence was that the term ‘carpenter’ passed for the term ‘engineer’ before industrialisation. They believe his father was an engineer of the age……

This is all cuckoo.

turn the page to cuckoo clocks.

Just look at it this way.. before we could calculate time science would be hearsay.. the greater the accuracy.. well, need In say more?

macx said:

A Brief History of Atomic Clocks at NIST

http://tf.nist.gov/cesium/atomichistory.htm

“1999 — NIST-F1 begins operation with an uncertainty of 1.7 × 10-15, or accuracy to about one second in 20 million years, making it one of the most accurate clocks ever made (a distinction shared with similar standards in France and Germany).”

…and there are today even more accurate clocks, but they have not (yet) been adopted as “standards” because they do not have the “history” of the Caesium beam clocks. eg hydrogen maser, quantum dot technology etc.

macx

They are indeed an impost to wear on the wrist.

roughbarked said:

roughbarked said:

Riff-in-Thyme said:

the revised opinion based upon substantial evidence was that the term ‘carpenter’ passed for the term ‘engineer’ before industrialisation. They believe his father was an engineer of the age……

This is all cuckoo.

turn the page to cuckoo clocks.

Just look at it this way.. before we could calculate time science would be hearsay.. the greater the accuracy.. well, need In say more?

the wheel wasn’t the bit we needed huh? bloody pendulums(excuse the battle muck)

A magnificent article from NIST re “clocks”

http://tf.nist.gov/general/pdf/2039.pdf

…and lots of piccy’s.

macx

macx said:

A magnificent article from NIST re “clocks”

http://tf.nist.gov/general/pdf/2039.pdf

…and lots of piccy’s.

macx

measurement uncertainty evaluations. awesome phrase

Riff-in-Thyme said:

roughbarked said:

roughbarked said:

This is all cuckoo.

turn the page to cuckoo clocks.

Just look at it this way.. before we could calculate time science would be hearsay.. the greater the accuracy.. well, need In say more?

the wheel wasn’t the bit we needed huh? bloody pendulums(excuse the battle muck)

I take your point but the wheel was long in use before the adaptation.

Riff-in-Thyme said:

macx said:

A magnificent article from NIST re “clocks”

http://tf.nist.gov/general/pdf/2039.pdf

…and lots of piccy’s.

macx

measurement uncertainty evaluations. awesome phrase

deep.

roughbarked said:

Riff-in-Thyme said:

roughbarked said:

Just look at it this way.. before we could calculate time science would be hearsay.. the greater the accuracy.. well, need In say more?

the wheel wasn’t the bit we needed huh? bloody pendulums(excuse the battle muck)

I take your point but the wheel was long in use before the adaptation.

it’s the work horse but we got a bit hypnotised with travelling on them everywhere

Riff-in-Thyme said:

roughbarked said:

Riff-in-Thyme said:

the wheel wasn’t the bit we needed huh? bloody pendulums(excuse the battle muck)

I take your point but the wheel was long in use before the adaptation.

it’s the work horse but we got a bit hypnotised with travelling on them everywhere

wouldn’t you?

>>>measurement uncertainty evaluations. awesome phrase

It is, and especially when one knows what it means!

macx

roughbarked said:

Riff-in-Thyme said:

roughbarked said:

I take your point but the wheel was long in use before the adaptation.

it’s the work horse but we got a bit hypnotised with travelling on them everywhere

wouldn’t you?

you mean “didn’t I bloody ever!!” Bit over tearing it up from one place to another these days though……..

macx said:

>>>measurement uncertainty evaluations. awesome phrase

It is, and especially when one knows what it means!

macx

and applies it as ones most fundamental self analysis tool……..

Riff-in-Thyme said:

roughbarked said:

Riff-in-Thyme said:

it’s the work horse but we got a bit hypnotised with travelling on them everywhere

wouldn’t you?

you mean “didn’t I bloody ever!!” Bit over tearing it up from one place to another these days though……..

take a beer, cool off between each phase.. one beer is usually enough.

Riff-in-Thyme said:

macx said:

>>>measurement uncertainty evaluations. awesome phrase

It is, and especially when one knows what it means!

macx

and applies it as ones most fundamental self analysis tool……..

and people think I talk crap.

try applying this to my posts, in evaluation.

Recloaks and re-enters sub space.

BBL

macx

roughbarked said:

Riff-in-Thyme said:

roughbarked said:

wouldn’t you?

you mean “didn’t I bloody ever!!” Bit over tearing it up from one place to another these days though……..

take a beer, cool off between each phase.. one beer is usually enough.

if it is coopers celebration ale I can’t really stop till I’ve guzzled six. they are bastard arse enablers I say!!!!!

macx said:

Recloaks and re-enters sub space.

BBL

macx

was good seeing you. :)

macx said:

Recloaks and re-enters sub space.

BBL

macx

hate it when he does that. always wonder what his missus must look like if he takes that much trouble to hide her whereabouts……

Riff-in-Thyme said:

macx said:

Recloaks and re-enters sub space.

BBL

macx

hate it when he does that. always wonder what his missus must look like if he takes that much trouble to hide her whereabouts……

I’d try not to elaborate, if I was you.

roughbarked said:

Riff-in-Thyme said:

macx said:

Recloaks and re-enters sub space.

BBL

macx

hate it when he does that. always wonder what his missus must look like if he takes that much trouble to hide her whereabouts……

I’d try not to elaborate, if I was you.

He’s probably just doing it for the kids……

> You should use something like this… http://www.jaycar.com.au/productView.asp?ID=ZL3555
> you could have the timed output of one 555 timer linked to another 555 timer, as the first timer pulses whatever it also pulses a voltage on the trigger input of another 555 timer

Both of those are exactly what I am using. The time delay for a 555 timer is ln(3)*R*C. Hence the problem.

This link might help.
http://www.sengpielaudio.com/calculator-parallel.htm

Molly, what is the output driving?

I have one or two of these things kicking around I can drop in the mail for you:

http://www.unitronics.com/plc-hmi/micro-oplc/m90-m91-
http://www.unitronics.com/Downloads/Support/Technical%20Library/M90M91%20Hardware/M90%20-%20Specifications/M90-T.pdf

You should be able to get them to operate an output to whatever time you want to 10ms accuracy.

Hmmm… reading the question, I am not sure it will do what you want.

I do not think you could build something that accurate with the hardware you’re looking at without temperature control and trimpots.

mollwollfumble said:

This is a straightforward maths question, for solving an electronic problem.

The time delay of a timer is given as 1.1*R*C where the time is in seconds, resistance R in ohms and capacitance C in farads. I want to get a time delay between 3.95 and 4 seconds.

I have 6 capacitors with sizes (in microFarads) 4.7, 10, 22, 33, 47, 100
Resistors (in kOhms) come in sizes 39, 47, 56, 68, 82, 100,120, 150, 180, 220, 270, 330, 390, 470, 560, 750, 1000

How many of the 6 capacitors can be used to get that time delay with one resistor? For each of the 6 capacitors what pair of resistors in parallel (if possible) will give the correct time delay?

Set it up in Excel, looks like four possibilities.
22 microFarads with 330 & 330 kOhm in parallel – 3.99 seconds
33 microFarads with 220 & 220 kOhm in parallel – 3.99 seconds
47 microFarads with 100 & 330 kOhm in parallel – 3.96 seconds
100 microFarads with 39 and 470 kOhm in parallel – 3.96 seconds

Give or take the accuracy of the resistors (eg. 1%, 5%) and capacitors.
What’s the accuracy of typical electrolytic capacitors?

PS. I am aware of Klipstein’s Law of Specification: In specifications, Murphy’s Law supersedes Ohm’s.

Carmen_Sandiego said:

Molly, what is the output driving?

I have one or two of these things kicking around I can drop in the mail for you:

http://www.unitronics.com/plc-hmi/micro-oplc/m90-m91-
http://www.unitronics.com/Downloads/Support/Technical%20Library/M90M91%20Hardware/M90%20-%20Specifications/M90-T.pdf

You should be able to get them to operate an output to whatever time you want to 10ms accuracy.

Ooh nice. A bit heavy for me though, I need to fit this in a rocket nosecone. The timer is for setting off rocket stages.

mollwollfumble said:

Give or take the accuracy of the resistors (eg. 1%, 5%) and capacitors.
What’s the accuracy of typical electrolytic capacitors?

PS. I am aware of Klipstein’s Law of Specification: In specifications, Murphy’s Law supersedes Ohm’s.

Electrolytic caps are generally around +/- 20%, but should be marked on the package.

Using a 555 for long times (more than about 250ms) is a bad idea. The accuracy decreases considerably as the time increases.

The 12 dollar arduino mini will give accuracy to 1 millisecond , it can control servos after all

It’s only 12 bucks

Wocky said:

mollwollfumble said:

Give or take the accuracy of the resistors (eg. 1%, 5%) and capacitors.
What’s the accuracy of typical electrolytic capacitors?

PS. I am aware of Klipstein’s Law of Specification: In specifications, Murphy’s Law supersedes Ohm’s.

Electrolytic caps are generally around +/- 20%, but should be marked on the package.

Using a 555 for long times (more than about 250ms) is a bad idea. The accuracy decreases considerably as the time increases.

What about a 555 triggering addition on a calculator chip? When output number = (your time) equivalent, then trigger job.

>Ooh nice. A bit heavy for me though, I need to fit this in a rocket nosecone. The timer is for setting off rocket stages.

:) always wished had been involved in rocketry as a hobby.

Good luck!

> Electrolytic caps are generally around +/- 20%, but should be marked on the package.

Ah, in that case Murphy’s law does supersede ohms. Unless they’re very temperature sensitive it looks like a case of try resistor combinations until I get the timing I want. Not much point in insisting on 1% resistor accuracy then.

> :) always wished had been involved in rocketry as a hobby.

There’s no time like the future. Had no interest in it earlier, would still have no interest in ground launch if I hadn’t calculated that it was possible to get into space for less than the price of a typical car. Now I’ve cut that price down to about $500. I still have to prove that the method works, though.

mollwollfumble said:

There’s no time like the future. Had no interest in it earlier, would still have no interest in ground launch if I hadn’t calculated that it was possible to get into space for less than the price of a typical car. Now I’ve cut that price down to about $500. I still have to prove that the method works, though.

It’s been interesting watching the progress.

Spiny Norman said:

mollwollfumble said:

There’s no time like the future. Had no interest in it earlier, would still have no interest in ground launch if I hadn’t calculated that it was possible to get into space for less than the price of a typical car. Now I’ve cut that price down to about $500. I still have to prove that the method works, though.

It’s been interesting watching the progress.

Pics or it didn’t happen ;)

poikilotherm said:

Spiny Norman said:

mollwollfumble said:

There’s no time like the future. Had no interest in it earlier, would still have no interest in ground launch if I hadn’t calculated that it was possible to get into space for less than the price of a typical car. Now I’ve cut that price down to about $500. I still have to prove that the method works, though.

It’s been interesting watching the progress.

Pics or it didn’t happen ;)

Spiny Norman said:

poikilotherm said:

Spiny Norman said:

It’s been interesting watching the progress.

Pics or it didn’t happen ;)

!http://upload.wikimedia.org/wikipedia/commons/4/44/Apollo_17_launch.jpg

That cost $500?

poikilotherm said:

Spiny Norman said:

poikilotherm said:

Pics or it didn’t happen ;)

!http://upload.wikimedia.org/wikipedia/commons/4/44/Apollo_17_launch.jpg

That cost $500?

Yep.
Moll is a great worker.

poikilotherm said:

mollwollfumble said:

There’s no time like the future. Had no interest in it earlier, would still have no interest in ground launch if I hadn’t calculated that it was possible to get into space for less than the price of a typical car. Now I’ve cut that price down to about $500. I still have to prove that the method works, though.

Pics or it didn’t happen ;)

Pics.

Black powder hobby rockets to 6 km altitude.

xkcd’s take on impossibility of black powder hobby rocket to 100 km altitude

Composite hobby rockets to 400 km altitude.