Sensing ambient light

[audioguru]

Hi Transistor,
Why do you have a high watt fluorescent tube on your rooftop?
Don't your streets have lights?

 

[transistor495]

Yes!
Apart from that we will use. Especially on areas where street light is away from the house. Moreover I feel it like a formality here

 

[audioguru]

Hi Transistor,
You are in a different world than me since you have a high Watt fluorescent light on your roofttop as a formality.

All streets in my city are lighted properly. A few people have a light on the front of their house at night but I don't unless someone is coming to visit.
A few people have a motion sensor light on the front of their house.

 

[premkumar9]

Good Idea. Those guys want you to succeed, because when you do, they do

Checked up with the manufacturer. Those negative pins are internally connected.

 

[premkumar9]

Or talk to the Application Engineers. In either case, that may be your best route to go. The people that design, or sell the product know best... Usually.

You could always use a current loop or something.

Can I switch ON/OFF FET IRFZ44N directly (through resistor) from the output pin of 89C2051 microcontroller?

 

[Gayan Soyza]

Ikalogic did many experiments on how to sense ambient lights.

He has detailed explained in his articles.

**broken link removed**

 

[kchriste]

Can I switch ON/OFF FET IRFZ44N directly (through resistor) from the output pin of 89C2051 microcontroller?

No. You need a logic level FET for this. A IRLZ44 will work.

 

[premkumar9]

No. You need a logic level FET for this. A IRLZ44 will work.

Is this OK for IRLZ44

 

[Mikebits]

If Kchriste suggested it then I would say your good to go.

 

[premkumar9]

If Kchriste suggested it then I would say your good to go.

He didn't suggest. I am just asking.

 

[Mikebits]

No. You need a logic level FET for this. A IRLZ44 will work.

He didn't suggest. I am just asking.

Oh, but I think he did... I think your ok with that fet.

 

[premkumar9]

Oh, but I think he did... I think your ok with that fet.

He suggested the FET. Then asked whether this circuit is OK for this FET

 

[premkumar9]

No. You need a logic level FET for this. A IRLZ44 will work.

Is this OK for IRFZ44 (IRLZ44 is not available with me)

 

[kchriste]

Eliminate R7 if the 12V isn't going any higher; The gate is good to 20V, but it's nice to have some headroom if needed. Because the 89C2051 can only source 80uA at 2.4V, you should also increase the value of R6 to 10K or so, but this will slow the switching time of the circuit somewhat. I'm not that familiar with the 89C2051, but you may have to add a pull up resistor on the IO pin to supply enough current for the transistor if you want faster switching speeds. How fast do you need to switch the load on and off?

 

[premkumar9]

Eliminate R7 if the 12V isn't going any higher; The gate is good to 20V, but it's nice to have some headroom if needed. Because the 89C2051 can only source 80uA at 2.4V, you should also increase the value of R6 to 10K or so, but this will slow the switching time of the circuit somewhat. I'm not that familiar with the 89C2051, but you may have to add a pull up resistor on the IO pin to supply enough current for the transistor if you want faster switching speeds. How fast do you need to switch the load on and off?

I didn't know that sourcing current of 89C2051 Pin is only 80uA (I thought up to 1mA may not be a problem). In fact 89C2051 has 2 open drain pins which I wanted to use for some other purpose. So in this case I will solve this problem by using one of those pins as shown. It has a sinking current of 20 mA. Is it correct to connect a pull up resistor to the O/P pin when it is not open drain?

 

[audioguru]

Simply look on the datasheet for the AT89C2051 micro-controller to see that its max allowed voltage on any pin is +7.0V and that your R9 is connected to +12V which might destroy it.

R9 should be connected to the +5V supply of the micro-controller.

Since you cannot get a logic-level Mosfet then test many of the ordinary Mosfets to find one that works with an input of 5V.

 

[premkumar9]

Simply look on the datasheet for the AT89C2051 micro-controller to see that its max allowed voltage on any pin is +7.0V and that your R9 is connected to +12V which might destroy it.

R9 should be connected to the +5V supply of the micro-controller.

Since you cannot get a logic-level Mosfet then test many of the ordinary Mosfets to find one that works with an input of 5V.

Can you pls send that data sheet?

 

[audioguru]

I got that one and get millions of other datasheets from Datasheet Archive - Free Datasheet Search Engine :: PDF Datasheets :: Data Sheet :: Datasheet :: Application Note : çš„å￾‚æ•° : 规格书 : 技术资料 : ë￾°ì￾´í„°ì‹œíŠ¸ : データ・シート : Fiche technique : Datenblatt : опиÑ￾ание .
They have a limit of about 25 per day but my router gives them a different address each time so I have no limit.

 

[premkumar9]

I got that one and get millions of other datasheets from Datasheet Archive - Free Datasheet Search Engine :: PDF Datasheets :: Data Sheet :: Datasheet :: Application Note : çš„å￾‚æ•° : 规æ*¼ä¹¦ : 技术资料 : ë￾°ì￾´í„°ì‹œíŠ¸ : データ・シート : Fiche technique : Datenblatt : опиÑ￾ание .
They have a limit of about 25 per day but my router gives them a different address each time so I have no limit.

I have the data sheet of ATMEL and I couldn't find this 7V limit on all pins. That is why I asked. A useful discussion was going on. I think it is better to avoid posts just for the sake of increasing counts.

 

[premkumar9]

I have the data sheet of ATMEL and I couldn't find this 7V limit on all pins. That is why I asked. A useful discussion was going on. I think it is better to avoid posts just for the sake of increasing counts.

Yes I have seen that the max voltage rating for any pin given as 7V. Thank you.