Toggle on of with timer555 and relay 2 different voltages with relay HELP

Thread Starter

rastaman46

Joined Nov 17, 2011
75
Toggle on of with timer555 and relay 2 different voltages with relay HELP



Timer 555 and relay circuit with 2 different powers


Hello im got circuit made of that image all works fine

im using two power feeds

one is 5V
Other is 12V

both can be run on same GND




but i want insert spdt relay in it to be able to turn 12v ground to relay so i get 12v of relay to my motor

ne555 is on 5v

i try but bad luck

once im switch power on its pover coil up all ok but im cant tur in off by pressing same momentary button i need disable graund manually to set relay to N-O position when relay on im got N-C


can any one help please
 

t_n_k

Joined Mar 6, 2009
5,455
Not exactly sure of your problem but - this seems to work in simulation mode.

Is your relay a 12V coil type as I have assumed?

The resistance (R5) shown in series with the relay coil is meant to be the coil resistance - not a separate resistor.

The relay contacts would then be used to toggle switch the 12V supply to the motor.
 

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Last edited:

Wendy

Joined Mar 24, 2008
22,138
Use a 5VDC relay. The contacts of the relay will handle the 12VDC side.

That, or connect the + side of the relay to +12V, the transistor will switch to ground.

*****************************************************

I started to give a long winded answer that had nothing to do with what you were talking about.

555 Bistable Multivibrator
 
Last edited:

praondevou

Joined Jul 9, 2011
2,942
Yes, just replace the 5VDC with 12VDC. The 555 and transistor can handle these voltages. Don't forget the freewheeling diode on your motor.
 

Thread Starter

rastaman46

Joined Nov 17, 2011
75
Hello im back again :(

if im run 12v true circuit and connect 12v device on end on it its just stop work correctly

"Dont go off buy one click" need press it from 10 to 20 times to get it off
did my resistors cause it or device drain it to much device is only one amp
 

Wendy

Joined Mar 24, 2008
22,138
Show us your current schematic.

Do you have any filter caps on this setup?

Have you measured your 12V power supply when it switches?

First guess, you are having a massive dropout of power supply voltage when your remote device is turned on. How much current does it pull.

This being a form of flip flop it will be sensitive to power supply fluctuations.
 

SgtWookie

Joined Jul 17, 2007
22,210
You need to have an 0.1uF cap and a larger (1uF or higher) cap across the power supply pins of the 555 timer. You also must have a diode connected across the coil of the relay, or else when you turn the transistor off, there will be a high voltage spike from the relay that will kill the transistor. It will also upset the 555 timer.

You probably have a lot of noise on your supply to your timer when the motor is on, which is why it keeps switching back on when you try to turn it off.
 

Thread Starter

rastaman46

Joined Nov 17, 2011
75
Thanks for quick replay

my schematics is this but instead 5V its on 12V and im avoid 2N3904 (that pas just 3.3V if im wright)



im got 10uf cap on im tryd 1000uf cap still the same works well with LEDS but not with fan on

im just test voltage drop yes im got just 8V instead 12v when ip plug the fan on i can see leds change brightness.
 

Wendy

Joined Mar 24, 2008
22,138
It is entirely possible your relay is dropping out. You could use a transistor (either BJT or MOSFET) to turn the motor on instead. You will need the swamping diode as with the relay.

What is the current of the motor?
 

Thread Starter

rastaman46

Joined Nov 17, 2011
75
motor is DC12V 0.40A 2X


but im check with with multimeter

Motor and one LED on im got 8.85V

Motor 2 LED on im got 7.95V

im not use relay now because circuit start relay but when circuit off by button relay still stays on

Did 10K can cause it? (for power drop or resistance)

Sorry for nooby questions but just starting in "K and Ohm" world
 
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