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i have a timing preoblem Answered

ok i have this solenoid. adn i want it so when i hit the power button i want it to start moving for a certin amount of time. then turn off. even if i hold the button for longer then tht set time. FOR EXAMPLE i push the power button and hold it for 2 seconds but i want the noid to act for one second. basically i need consistency how do i do i do this with out a mivcro proseser. is their a timming cuircuit i can adapt to what i need?

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fretmelter
fretmelter

13 years ago

ok well here is what i want to do is a solenoid tht reqires 6volts with a 555 timer circuit so when i press the power button it only goes one for a certain time. and i am using a 9 volt to power it but only getting 4 volts at the place where i put the noid

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gmoon
gmoon

Reply 13 years ago

Using the transistor as a switch is what you need. You can use separate power supplies (different voltage), so long as they share a common ground.

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fretmelter
fretmelter

Reply 13 years ago

can i put a transistor right to the noid lead and the ground? to it goes from like 4 to araound six?

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gmoon
gmoon

Reply 13 years ago

Pretty much. Read the link on transistor switches I quoted before.

You'll need the load current (RL) on the diagram--use a VOM in series with the solenoid to find that. The hfe of a 2n2222 isn't listed on that page, it's about 30. The 2n2222 should handle 1/2 amp without a heatsink--should be enough for a 6V solenoid.

You just need to figure the value of Rb. For example:

If your solenoid draws 150 mA (0.15 ams) at 6V, and the 555 output is 4V--

Rb = (4 * 30) / (5 * 0.15)

or 160 ohms for Rb.

I honestly don't think inserting the value of 5 is too high, resulting in an inefficient value for Rb--I would start around 1K ohm, and work my way lower. If you want to 'hack' the circuit, that's the easiest way to do it--no math, just start with a 4.7K resistor (this value depends on the load current of the device) and work down.

DO insert the protection diode, as referenced.

I edited the picture from the site a little to help...

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gmoon
gmoon

Reply 13 years ago

EDIT: "I honestly think inserting the value of 5 is too high...."

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gmoon
gmoon

Reply 13 years ago

Here's the diagram...

trswinpn.jpg
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fretmelter
fretmelter

13 years ago

ok i have done some research and i have done some in the past....BUT cann i give out 6V for my noid cuz the voltage is stepped down a ton. to like 3 volts to power things like a LED

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gmoon
gmoon

Reply 13 years ago

I'm not reading you--your working voltage is 3V and you need to power a solenoid, OR your voltage is 6V and you want reduce that?

If you're powering a solenoid (or motor) with a lower voltage device, just use a transistor switch (look specifically at the relay control and the protection diode you will need for an electromechanical device like a solenoid.) You could get fancy with a FET, but a trusty ol' 2N2222 NPN bipolar transistor shouldn't cost you more than 10 cents. They can handle up to 1 amp with a heat sink....

Here's a one-shot 555 circuit that has a fixed duration, regardless of the duration of the button press.

Honestly, though--these circuits are REALLY easy to find with google or whatever. If the circuits linked above don't fit your needs, you can find ten thousand more with simple searches like "transistor switch"...

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NachoMahma
NachoMahma

13 years ago

. I think what you are looking for is called a one-shot - the output is on for the same amount of time, no matter how long the input is on. I don't know how to build 'em, just used 'em at work.

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NachoMahma
NachoMahma

Reply 13 years ago

. Or use a time-delay-off relay. Use one of the NC contacts to block the input switch when the relay is energized.

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HamO
HamO

13 years ago

Timing is not even your only problem!

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fretmelter
fretmelter

13 years ago

do 555 timers delay the voltage too?

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gmoon
gmoon

13 years ago

You can search for '555 timer' here in instructables, or on the greater web itself. You'll find more than you need....