create a 10 sec delay in a circuit - Page 1
Forum section: electronics / beginners

author: cyxstudio
author_rank: Newbie
timestamp: May 01, 2012, 05:12:27 pm
content: hi i am very new to electronics...i wish to create a circuit that has a 10 sec delay the moment the circuit is close before the load starts working. i was told that a simple resistor - capacitor circuit will do the job i tried but it doesnt work. i did some googled and some says it involves IC 555 and transistors. Can someone help me with this? thanks.

author: IanB
author_rank: Super Contributor
timestamp: May 01, 2012, 05:27:53 pm
content: This is simple to do, but...what are the power requirements of your load? What voltage and current? Any circuit like this always has two parts: one part is producing the 10 second delay, the other part is switching the load.

author: MikeK
author_rank: Super Contributor
timestamp: May 01, 2012, 05:56:23 pm
content: Also, you said that your RC circuit didn't work. You'd probably learn a great deal by posting a schematic of it so that we can tell you how it does or doesn't work.

author: olsenn
author_rank: Frequent Contributor
timestamp: May 01, 2012, 06:05:13 pm
content: QuoteActually you may get away without the transistor... the 555 timer is capable of sourcing a surprising amount of current. Take a look at the below wikipedia article on the 555 timer. In monostable mode you can get a 10s pulse and in astable mode you can get a square waveform (repeating 10s pulses) with a selectable duty cycle.You can certainly use passive components (resistors and capacitors) to do this, but be careful... first of all this won't produce a square wave, the voltage will decrease slowly over time, and the resistance/capacitance required to obtain such a slow droop may not be feasible for your circuit. You could also use an RC circuit and a comparator to determine when 10s is up, but I'd still say the 555 timer is your best option.

author: TerminalJack505
author_rank: Super Contributor
timestamp: May 01, 2012, 06:12:00 pm
content: If you are new to electronics then the 555 timer is probably the way to go. You can basically just 'cookbook' it. You can find a similar circuit that does what you need and use this as a 'recipe' and tweak it as appropriate.You can achieve the same thing with fewer parts but then you will need to know a little more than you might be able to handle right now.

author: cyxstudio
author_rank: Newbie
timestamp: May 02, 2012, 09:53:56 am
content: Quote from: IanB on May 01, 2012, 05:27:53 pma 9V - 12 V motor, im using the standard 9v dc cell to power it.

author: cyxstudio
author_rank: Newbie
timestamp: May 02, 2012, 10:01:31 am
content: Quote from: MikeK on May 01, 2012, 05:56:23 pmthe motor didnt rotate at all = (

author: IanB
author_rank: Super Contributor
timestamp: May 02, 2012, 01:49:07 pm
content: Quote from: cyxstudio on May 02, 2012, 10:01:31 amNo, it wouldn't. There is far, far more you need to understand about circuits before you can design a circuit to do what you ask. You should use Google and see if you can find an example of a working circuit to build using a 555 timer IC.

author: T4P
author_rank: Super Contributor
timestamp: May 02, 2012, 07:39:10 pm
content: Um ... that's all wrong . Capacitors block DC voltage and by the time it's charged up the circuit goes open circuit .Look for PWM timers like 555 and you will be on the right track . Something that would toggle between on and off (PWM) that can be set with a RC circuit or maybe even not , just a pot would make better sense .http://pcbheaven.com/circuitpages/LED_PWM_Dimmer/If you motor is at least 3W ( i doubt so ) then use a 1Amp transistor

author: Mr J
author_rank: Regular Contributor
timestamp: May 05, 2012, 03:02:18 pm
content: try looking athttp://www.n1ir.com/2011/03/cqd-experience-ignition-switch.htmlthis will give you some ideas with a 555 timer

author: Zero999
author_rank: Super Contributor
timestamp: May 05, 2012, 04:13:02 pm
content: Quote from: cyxstudio on May 02, 2012, 09:53:56 amHow big is the motor?What size is the 9V battery?How long do you want it to run for off the same battery?