EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: cyxstudio on May 01, 2012, 05:12:27 pm
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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.
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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.
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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.
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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.
Actually 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.
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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.
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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.
a 9V - 12 V motor, im using the standard 9v dc cell to power it.
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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.
the motor didnt rotate at all = (
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the motor didnt rotate at all = (
No, 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.
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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/ (http://pcbheaven.com/circuitpages/LED_PWM_Dimmer/)
If you motor is at least 3W ( i doubt so ) then use a 1Amp transistor
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try looking at http://www.n1ir.com/2011/03/cqd-experience-ignition-switch.html (http://www.n1ir.com/2011/03/cqd-experience-ignition-switch.html)
this will give you some ideas with a 555 timer
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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.
a 9V - 12 V motor, im using the standard 9v dc cell to power it.
How big is the motor?
What size is the 9V battery?
How long do you want it to run for off the same battery?