Using Solid State Relay to Light up a Bulb

[ke5frf]

Now whats this?? Do i need to add something to ke5frf's latest diagram?

He is advising something that is a SAFETY FEATURE, a fuseable link. Somewhere between the line wire from the cord and the line input on the relay, it would be a GOOD IDEA to add a FUSE for safety. If a short circuit occurs, this will OPEN the circuit like a switch to prevent electric shock. This is not critical to the function of your project, but will add a dimension of safety to it.

VERY GOOD ADVICE. I apologize for not adding it to the drawing.

Oh and yes, the switch on the DC power supply is interchangeable with any on/off method including a microcontroller command.

 

[raziiq]

Ok thank you for bearing with a noob, thanks for all your help, i think i am ready to go in practical with my Project now.

Your help is really appreciated

 

[Sceadwian]

Before you go practical you need to determine if the Arduino output can supply enough current to trigger the SSR. I was unable to find a datasheet for your relay, but the current required can be a bit higher than a typical IO port MAY be capable of, you can try it but it's something you need to be aware of and quantify at some point. You may need to use a pass transistor to supply the relay, it's not a bad idea anyways as it's always a good idea to load the I/O pins on an MCU as little as possible. Leads to a whole lot fewer headaches down the road when you suddenly run out of current on an I/O or worse the entire module.

 

[raziiq]

Arduino pin delivers 40mA of current, i think it should be ok to use with SSR, or should i somehow calculate the amount of current required for SSR to operate?

 

[Sceadwian]

It should be listed in the datasheet of the PDF, 40ma is probably enough.
But the Arduinos current limits are more complicated than that. It may be X number of MA's per pin on a specific set of I/O lines but the TOTAL modules current is also limited. You could be using 40-60% of the entire possible current output of the Arduino on that one relay, adding more things at that point will cause strange reactions or chip damage. This is why transistor bypass circuits are very commonly used on such devices.

 

[raziiq]

Ok, so its a good idea to use a Transistor in between SSR and Arduino, since i am playing to add more Relays to other pins of Arduino in Future?

 

[Sceadwian]

Yes, absolutely.

 

[raziiq]

Ok thank you, BTW whats your say on this Relay

**broken link removed**

I am interested in AQG12105

You can see the Picture on the Basic Information Tab

 

[Sceadwian]

The key you're looking for there is the input impedance which is 300 ohms.
So it'll draw 14ma at 4 volts and 20ma at 6 volts. So figure worst case scenario is 20ma. A single IO line could probably do it, but I think most AVR's are limited to around 100ma for the whole chip, and no more than so much can be on any single I/O port. a resistor into the base of a general purpose switching transistor will saturate for that kind of load at well under 1ma, so just pick your base resistor appropriately. At 5V's supply a 5k resistor should do it to any general purpose transistor.

 

[raziiq]

BTW what kind of wires do you recommend for this project?

I am thinking of using the Normal LAMP wire. I ll cut it and use it between SSR and AC Voltage and use the simple BreadBoard(May be wires inside the LAN cable) between Arduino and SSR. is it OK?

 

[Sceadwian]

The contacts on a breadboard are only rated for about 1amp of current, anything more than that is going to have to be done off the breadboard on perfboard with a soldering iron and jumper wires or something similar. With the extra capactiance that's part of a breadboard I wouldn't really recommend wiring AC directly to it. It's really not that hard to point to point solder on perf board or use something like vero board.

 

[raziiq]

thanks for the reply.

BTW what if i use a SSR which will give me a current output of only 1A MAX, as i need to light up a bulb which is only 60WATT and according to the following

P = IE
I = P/E = 60/100 = 0.6A

So i think i can use a SSR with following attributes

IN: 4~7VDC
OUT: 100~220VAC
Current OUT : 1A Max

Whats your say on this?

 

[Sceadwian]

Depends on if the surge current when the bulb is light up cold will destroy the SSR or not. The initial current through an incandescent is several times it's running current.

 

[mneary]

Smaller SSRs won't protect the breadboard.

The contacts will receive whatever the lamp needs. 120V on a breadboard could be dangerous, regardless of the current. There's a risk of accidentally touching the back of the contacts. Your lamp cord won't fit into the breadboard anyway.

I also recommend wiring off-breadboard for all AC mains.

 

[raziiq]

Smaller SSRs won't protect the breadboard.

The contacts will receive whatever the lamp needs. 120V on a breadboard could be dangerous, regardless of the current. There's a risk of accidentally touching the back of the contacts. Your lamp cord won't fit into the breadboard anyway.

I also recommend wiring off-breadboard for all AC mains.

Thanks for the reply. I was talking about using the AC Lamp wires Off-Breadboard and 5VDC wires on-Breadboard, but then i decided not to use the breadboard at all.

Thanks for the suggestion.

 

[raziiq]

BTW its a good idea to solder the AC wires before connecting them to SSR? Is it safe and recommended?

 

[mneary]

I prefer to use solderless crimp terminals. When properly assembled they contain all of the fine strands and prevent short circuits.

Soldering the wires (called 'tinning') keeps all the strands contained and initially looks like a good idea. Unfortunately solder is soft, and a tight connection today is falling apart tomorrow.

 

[Mark_R]

BTW,
not a problem with the light bulb being contemplated, but on future applications, pay attention to the minimum load requirements of the solid state relays. Not drawing enough current can cause erratic switching. This bit me in the butt once.