Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Controlling 240v with 5v

Status
Not open for further replies.
G

gonadgranny

Member level 4
Joined
Feb 23, 2011
Messages
68
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,286
Activity points
1,930
Hi. I would like to be able to control mains powered (240v) bulbs using a 5v current. I believe it is possible to do this using relays but am not quite sure which ones. It sounds like a fairly straight forward problem but don;t know where to start. Thanks.
Danny.
 

Check out the ST Micro ACS102-6TA if your bulbs are under 40 watts. This part is rated up to 600V at 0.2 amps.
 
Yes it's posible to control it using triac. just google search dimmer circute.
 
thank you all ver much. i'll check it out.
 

Hey. would it be possible to connect the 5v signal to one of these relays - **broken link removed**
which is then connected to the mains?
thanks.
Dan.

---------- Post added at 16:12 ---------- Previous post was at 16:11 ----------

Hey. would it be possible to connect the 5v signal to one of **broken link removed** relays which is then connected to the mains?
thanks.
Dan.
 

gonadgranny said:
Hey. would it be possible to connect the 5v signal to one of these relays - **broken link removed**
which is then connected to the mains?
thanks.
Dan.

---------- Post added at 16:12 ---------- Previous post was at 16:11 ----------

Hey. would it be possible to connect the 5v signal to one of **broken link removed** relays which is then connected to the mains?
thanks.
Dan.
Click to expand...

It's all in the specs...

Max voltage: 250Vac/60Vdc
Max current (5A): 5A AC/DC 240Vac/24Vdc
Operating voltage range: 4.5V - 7.8V
Click to expand...

So, yes.
This looks to be a single-pole switch, so you will only be able to disconnect one "wire" from the load. Also, max current @ 220V is 5 amps.
 
Thanks. The specs suggested that it would indeed be possible but I am treading lightly so as not to ruin any of my electronics.

Would I need to add a diode in order to stop the "Backlash" which I heave heard about?
I have an arduino microcontroller connected to a transistor to provide the 5V signal which I don't want to fry.
Thank you.
Danny.
 

gonadgranny said:
Thanks. The specs suggested that it would indeed be possible but I am treading lightly so as not to ruin any of my electronics.

Would I need to add a diode in order to stop the "Backlash" which I heave heard about?
I have an arduino microcontroller connected to a transistor to provide the 5V signal which I don't want to fry.
Thank you.
Danny.
Click to expand...

Yes, you'll want to put a diode across the coil of the relay. The "backlash" you are talking about is often called "inductive kickback", but more correctly, it's back-EMF (electromotive force... aka voltage). Current in an inductor (coil) cannot change instantaneously, so when you disconnect power from a coil the magnetic field will begin to collapse, trying to keep the current flowing at the same rate. This creates a large neagative voltage potential, which can be tens of volts, which could be enough to cause damage to your transistor & microcontroller.

Look up at one of my older posts. I linked a thread that is doing about the same thing you are. In there is a link to a SparkFun article, also doing the same thing you are. It even has a nice little schematic.
 

Syncopator said:
The polarity depends on the particular circuit, and the voltage could be a lot higher than tens of volts.

Take a look at this explanation.
Click to expand...

No, the polarity doens't depend on the circuit. The voltage across an inductor comes from this fundamental differential equation: V = L * di/dt. If your time-rate of change of current through the inductor is negative (going from a finite DC current, to zero), then V is negative (di/dt is negative; times L, its still a negative value). The voltage across the terminals of the coil will most certainly be negative, however, the absolute value of that voltage, relative to the circuit ground, is dependant on the configuration of your circuit.
 

enjunear said:
No, the polarity doens't depend on the circuit. ..... the absolute value of that voltage, relative to the circuit groundsic, is dependant on the configuration of your circuit.
Click to expand...

Make your mind up.

enjunear said:
The voltage across the terminals of the coil will most certainly be negative...
Click to expand...

If one end of the coil is connected to a positive supply rail, the other end to a switch and the other side of the switch to 0V; when the switch opens the voltage across the coil will reverse, the negative being connected to the positive rail and the positive to the now open switch. Without a diode, that voltage will be considerably more positive than the positive supply rail.

To call that negative is indicative of muddled thinking. Very muddled indeed.

Methinks I have discovered yet another individual who likes to argue for argument's sake.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top