remote controled door 10 second delay

[Big zee]

hi there
im trying to build a remote controled door (so it can be open the lock)
i already got the remote control and the receiver and the solenoid and a relay and it does work.
but the problem is if im far away from the door the signal will open and close 4 time in a second as same as the solenoid .

all i need is circuit to keep it open for 10 second the its (the circuit) will shutdown.
it will be great if you help me with NE555 or so. because i dont want to use arduino for this one.
please help me to finish this project.
regards.

 

[redwire]

Did you look up 555 monostable mode?

 

[Big zee]

yes i did , but im not sure what the capacitor and resistors values to keep it for 10 sec.

 

[Hero999]

It's on the datasheet.
http://www.ti.com/lit/ds/slfs022h/slfs022h.pdf

 

[Big zee]

it didnt say but i found an app and its says 4.8uf and 1.8M ohm
thank you all.

 

[Hero999]

It does say on the datasheet, see figure 11 on page 10.

 

[Big zee]

sorry i didnt see this one . i was looking for something with maths. but that mean if i wnat 10s. then i have to use 1Mohm and 10uf but with the app says with this one will give me 11s.
im ok with these numbers . thanks a lot....

 

[Hero999]

sorry i didnt see this one . i was looking for something with maths. but that mean if i wnat 10s. then i have to use 1Mohm and 10uf but with the app says with this one will give me 11s.
im ok with these numbers . thanks a lot....

That's true but there's no point in trying to aim for any decent level of accuracy, when typical capacitors have a tolerance of 20%.

 

[Big zee]

Should I use ceramic capacitor or the other ones? And what will happen if I used the other ones?

 

[Hero999]

Most capacitors in this value range have poor tolerance/stability. Ceramics are probably the worst as far as stability is concerned. The capacitance drops as the bias voltage increases and they're often piezo electric, i.e. when they vibrate, they generate electricity. Electrolytic capacitors have very poor tolerance, typically -20%/+80%.

Polypropylene or polyester is probably best for this application as 5% tolerance is widely available and it has good stability.

 

[Big zee]

thanks a lot.
i got one last question...
pin 2 on the 555 the trigger can i connect the signal to it ?
when i use my project i connected the RF receiver to the relay with a single wire to open it but when i tried to connect that wire to pin 2 and the out (pin 3) to the relay it didnt work properly! do i have to ground something ?

 

[Hero999]

Did you use a back-EMF protection diode?

How much current does the relay take? You may need to add a transistor to drive the relay.

 

[Big zee]

no i didn’t use a diode !
and the relay already got a transistor and its open and closes without even a signal (this is 1st problem)!!!!
the second one is when i press the remote it won’t open .. but in some case when its open by its self and i press the remote it will still open until i remove my finger .... and all my parts is new.
should i use a diode from pin 3 (output) to GND ?
thx.

 

[redwire]

why don't you  connect a resistor and led to the output (pin 3) of the 555 first. You can visually see what's going on.  Then work in the relay.

 

[Hero999]

I agree with the above: you should test the 555 timer circuit first to be sure it works on its own.

If the relay is already being driven from a transistor, there's no need for a diode.

Have you connected the 0V rails of both circuits together? There needs to be a common 0V reference for the circuits to interface with one another.

If a pulse is applied to pin 2 for longer than the length of the delay, the output will stay high until the input goes low again. If this is a problem, you should AC couple pin 2 to the trigger signal via a small capacitor (100pF to 100nF) and bias it to +V with a pull-up resistor (10k to 1M).

See the application note linked below for more information:
http://www.doctronics.co.uk/pdf_files/555an.pdf

 

[Big zee]

Ok .. now it's work good . But I ran into another problem. My RF receiver will trigger the ne555 all the time and when I press the button it will turn it off until I release it.  How can I reverse it? (The signal not the receiver)

 

[Big zee]

noting ??

 

[Big zee]

should i use a transistor?