# Stabalizing output voltage from astable 555 circuit

#### wachanna

Joined May 26, 2021
12
Hello electron manipulators. I have a 555 and its wired up in astable mode, so it has a period on and a period off. When i measure the ouptut voltage with no load, it is same as input, but when attatched to a load, it drops a few volts. Since its a switch that repeatedly turns off and on, i dont know what to put at the output, or anywhere, to stabalize the output voltage. I have 12 volts on input and a 12 volt relay coil on the output, so, any ideas how to feed the relay coil with a solid 12 volts, in a simple and inexpensive way, will be greatly appreciated. Thanks

#### Papabravo

Joined Feb 24, 2006
16,459
Hello electron manipulators. I have a 555 and its wired up in astable mode, so it has a period on and a period off. When i measure the ouptut voltage with no load, it is same as input, but when attatched to a load, it drops a few volts. Since its a switch that repeatedly turns off and on, i dont know what to put at the output, or anywhere, to stabalize the output voltage. I have 12 volts on input and a 12 volt relay coil on the output, so, any ideas how to feed the relay coil with a solid 12 volts, in a simple and inexpensive way, will be greatly appreciated. Thanks
Stability and stabilization has nothing to do with anything you are talking about. So what do you want? You cannot have a stable output voltage and an astable output that alternates between GND and some output voltage. BTW - I'd be willing to bet that what ever output you are getting at the output it is the same on each and every cycle within a couple of millivolts. A 555 is not designed to drive heavy loads. How much current does your load require? Did you bother to read the datasheet? What does it say exactly? If you need to drive a heavy load you're going to need some more circuitry. First however you need to define your requirements.

#### ErnieM

Joined Apr 24, 2011
8,167
You need two more parts. Connect the relay to the 12 volts and the collector of the transistor. Ground the emitter. Connect the base thru a resistor to the 555's output.

If you use a suitable FET you can skip the resistor.

Oh, and if you intend to use this circuit more than once put a diode across the relay to catch the inductive spike it generates when you turn it off.

Sorry... sitting here on the shore of the Caribbean with just a tablet I can't post schematics.

#### wachanna

Joined May 26, 2021
12
You need two more parts. Connect the relay to the 12 volts and the collector of the transistor. Ground the emitter. Connect the base thru a resistor to the 555's output.

If you use a suitable FET you can skip the resistor.

Oh, and if you intend to use this circuit more than once put a diode across the relay to catch the inductive spike it generates when you turn it off.

Sorry... sitting here on the shore of the Caribbean with just a tablet I can't post schematics.
Is there an alternative way?

#### SamR

Joined Mar 19, 2019
3,448
Dropping voltage is generally a clue that the load is trying to use more current than the output voltage provides.

The solution to that is to supply a separate suitable voltage supply to the load that is turned on and off by a transistor. Preferably a low gate threshold voltage FET. In the case of the 555 this is not unusual.

#### wachanna

Joined May 26, 2021
12
Dropping voltage is generally a clue that the load is trying to use more current than the output voltage provides.

The solution to that is to supply a separate suitable voltage supply to the load that is turned on and off by a transistor. Preferably a low gate threshold voltage FET. In the case of the 555 this is not unusual.
Is there an alternative way?

#### SamR

Joined Mar 19, 2019
3,448
Don't use a 555 and design a power circuit?

#### Irving

Joined Jan 30, 2016
1,818
What relay are you using?

You've been told twice the correct <\$1 solution.

The only other realistic option is to use a low-current relay with a high-resistance coil. I'll bet your using a cheap automotive relay rather than one designed to be driven by a digital circuit. But that's potentially a much more expensive solution depending on what your relay is switching.

#### DickCappels

Joined Aug 21, 2008
7,533
If you NE555 can drive your relay, you are done. The relay contacts will be either open or closed, not somewhere dependent upon the drive current or voltage.

#### atferrari

Joined Jan 6, 2004
4,379
You need two more parts. Connect the relay to the 12 volts and the collector of the transistor. Ground the emitter. Connect the base thru a resistor to the 555's output.

If you use a suitable FET you can skip the resistor.

Oh, and if you intend to use this circuit more than once put a diode across the relay to catch the inductive spike it generates when you turn it off.

Sorry... sitting here on the shore of the Caribbean with just a tablet I can't post schematics.
Suffering as I can see.

#### wachanna

Joined May 26, 2021
12
Don't use a 555 and design a power circuit?
Could you provide an example of a "power circuit", please?

#### LowQCab

Joined Nov 6, 2012
725
Hello electron manipulators. I have a 555 and its wired up in astable mode, so it has a period on and a period off. When i measure the ouptut voltage with no load, it is same as input, but when attatched to a load, it drops a few volts. Since its a switch that repeatedly turns off and on, i dont know what to put at the output, or anywhere, to stabalize the output voltage. I have 12 volts on input and a 12 volt relay coil on the output, so, any ideas how to feed the relay coil with a solid 12 volts, in a simple and inexpensive way, will be greatly appreciated. Thanks
If you want a straight and useful answer,
you must provide ALL of the details on what You are trying to accomplish with this device.

Why are You using an Old-School-Relay ?
What is the Relay controlling ?
Why do You think that the Relay is not getting enough Voltage,
and what problem do You think that is causing ?

We need an accurate Schematic with Part-Numbers and Component-Values
so that we can have some sort of clue as to what problems you may be experiencing.

One Picture is worth a Thousand Words, sometimes more.

If You really need more Current for your Relay,
there's a sneaky way to double the Output Current of a 555,
but I have no clue about what You are trying to accomplish.
.
.
.

#### Papabravo

Joined Feb 24, 2006
16,459
This is like an old married couple trying to decide if divorce is the proper solution. Let me spell it out for you.....

#### AnalogKid

Joined Aug 1, 2013
9,283
That far South it is approaching the dead of winter. Suffering indeed.
The southernmost point of the Caribbean Sea is over 600 miles *north* of the equator. Unless I missed something, they are in full holy-crap-its-hot-out-here mode.

ak

#### Papabravo

Joined Feb 24, 2006
16,459
The southernmost point of the Caribbean Sea is over 600 miles *north* of the equator. Unless I missed something, they are in full holy-crap-its-hot-out-here mode.

ak
You missed my point entirely. @atferrari is from Argentina, which is most definitely in the Southern Hemisphere. I don't know what city he is from, but I imagine it is a port city, and not something exotic like Ushuaia, the capital of Tierra del Fuego.

It is Ranelagh, a suburb or Buenos Aires

#### atferrari

Joined Jan 6, 2004
4,379
You missed my point entirely. @atferrari is from Argentina, which is most definitely in the Southern Hemisphere. I don't know what city he is from, but I imagine it is a port city, and not something exotic like Ushuaia, the capital of Tierra del Fuego.

It is Ranelagh, a suburb or Buenos Aires
Part of Berazategui, few Km away from the River Plate more than 35º South Latitude. Winter commenced just few days ago.

#### Papabravo

Joined Feb 24, 2006
16,459
Part of Berazategui, few Km away from the River Plate more than 35º South Latitude. Winter commenced just few days ago.
That's about equivalent to Chatanooga, TN for those of us in the Northern Hemisphere.