driving LEDs with a Relay

[t.man]

Morning Mike,
Repost of the way the DIL 5V relay is connected, the pin # are the relay.

Personally I would have just used a transistor to drive the LED's.

what about this one or any suggetion?

 

[ericgibbs]

what about this one or any suggetion?

hi,
Looks OK, but you cannot drive three 2V Red LED's from 5Vdc supply.
Maximum is two, unless you use +12V, then it can be five 2V Red LED's.

OK.?

Attached dwg.

 

[t.man]

hi,
Looks OK, but you cannot drive three 2V Red LED's from 5Vdc supply.
Maximum is two, unless you use +12V, then it can be five 2V Red LED's.

OK.?

Attached dwg.

i'm using 13V 800mA plug pack but when i put my multimeter probes just before 78L05 i measure something like 16.5...V. can i use it to drive the LEDs?

 

[ericgibbs]

i'm using 13V 800mA plug pack but when i put my multimeter probes just before 78L05 i measure something like 16.5...V. can i use it to drive the LEDs?

hi,
If the 16.5Vdc stays close to that value, you could connect 6 or 7 Red LED's in series with suitable resistor and drive them with the transistor.

eg: 16.5V - [7 * 2Vdp]/0.015mA

thats 16.5 -14 = 2.5/0.015,,, = 166R, say 180R.

OK.?

 

[t.man]

hi,
If the 16.5Vdc stays close to that value, you could connect 6 or 7 Red LED's in series with suitable resistor and drive them with the transistor.

eg: 16.5V - [7 * 2Vdp]/0.015mA

thats 16.5 -14 = 2.5/0.015,,, = 166R, say 180R.

OK.?

i'll try to get some transistors so i try the idea....

above all i'll like to thank you a lot for your help...keep up that good work.

Kind regards,

 

[t.man]

hi,
Looks OK, but you cannot drive three 2V Red LED's from 5Vdc supply.
Maximum is two, unless you use +12V, then it can be five 2V Red LED's.

OK.?

Attached dwg.

Is 2N3904 the right part for this application?

 

[ericgibbs]

Is 2N3904 the right part for this application?

hi,
The 2N3904 has a maximum rating of 200mA, but I would use it at not more than 100mA or so.

How much current will the transistor be switching.?

 

[t.man]

hi,
The 2N3904 has a maximum rating of 200mA, but I would use it at not more than 100mA or so.

How much current will the transistor be switching.?

it'll be switching the circuit of 12V driving LEDs.

 

[ericgibbs]

it'll be switching the circuit of 12V driving LEDs.

Hi,
That dosn't tell me the current.

So assume the RED LED's are 2Vdp/LED, as you are using a 12V supply, this gives 5 LED * 2v =10Vdp per chain.

If you have one chain with a LED current of 15mA, this means you have to drop 2V at 0.015.
So you require a 133R resistor [ 120R] per chain.
So the current per chain with a 120R would be 2V/120R = 17mA

Using a 2N3904 transistor you could have 6 chains, in parallel giving a total collector current of 100mA.

Do you follow.?

 

[t.man]

Hi,
That dosn't tell me the current.

So assume the RED LED's are 2Vdp/LED, as you are using a 12V supply, this gives 5 LED * 2v =10Vdp per chain.

If you have one chain with a LED current of 15mA, this means you have to drop 2V at 0.015.
So you require a 133R resistor [ 120R] per chain.
So the current per chain with a 120R would be 2V/120R = 17mA

Using a 2N3904 transistor you could have 6 chains, in parallel giving a total collector current of 100mA.

Do you follow.?

yes, i think i get what you are saying.

currents in parallel add up to give a total current and
i can have 36 max no. of LEDs.

 

[ericgibbs]

yes, i think i get what you are saying.

currents in parallel add up to give a total current and
i can have 36 max no. of LEDs.

hi,
If you have 5 RED leds in each chain and have 6 chains, thats 6 *5 =30 LED's

Where does the 36 number come from.?

 

[t.man]

hi,
If you have 5 RED leds in each chain and have 6 chains, thats 6 *5 =30 LED's

Where does the 36 number come from.?

wow!....this is funny

i dont know my math!.

This reminds me the other time i was with a little Johnny...

me: "Johny, if u have R5.00 and your dad gives you R5.00, how much will you have?

Johnny: " R5.00!"

me: "Johnny, you dont know your math!.."

Johnny: "You dont know my dad!..."

 

[ericgibbs]

wow!....this is funny

i dont know my math!.

This reminds me the other time i was with a little Johnny...

me: "Johny, if u have R5.00 and your dad gives you R5.00, how much will you have?

Johnny: " R5.00!"

me: "Johnny, you dont know your math!.."

Johnny: "You dont know my dad!..."

As they say in RSA, a Rand in the hand is worth two in the Bush...

 

[t.man]

I'm thinking very hard about how i can arrange these LEDs( 2 groups of them, red and green) of mine on a PCB so they can make a nice visible cluster... rectangular, circular, running wires connecting LEDs to the PCB,..?

bearing in mind that there'll be casing of the circuit.

any idea?

 

[t.man]

hi,
The 2N3904 has a maximum rating of 200mA, but I would use it at not more than 100mA or so.

How much current will the transistor be switching.?

hi, i failed to get 2N3904. can u give a list of equivalents or any suitable for the work?

 

[ericgibbs]

hi, i failed to get 2N3904. can u give a list of equivalents or any suitable for the work?

hi,
The transistor description is:
General purpose 'npn' switching transistor,
Vce not less than 25V,
Collector current not less than 200mA,
Gain not less than 50.

There are dozens of equivalents.
Tell me what types are available at your location and I will suggest a suitable type.

 

[t.man]

hi,
The transistor description is:
General purpose 'npn' switching transistor,
Vce not less than 25V,
Collector current not less than 200mA,
Gain not less than 50.

There are dozens of equivalents.
Tell me what types are available at your location and I will suggest a suitable type.

just picked a couple OF npn transistor on a list

2N5109,2N1893,2N3053, 2N2222,2N2219,2N3439
BD139, BU126,BD437, BD139,TIP41C, TIP35C

 

[ericgibbs]

just picked a couple OF npn transistor on a list

2N5109,2N1893,2N3053, 2N2222,2N2219,2N3439
BD139, BU126,BD437, BD139,TIP41C, TIP35C

I use the 2N2222 as a preference, its a good allround transistor.