dome light dimmer (with delay) - Page 2

kronos · 11-09-2005, 12:38 PM

Quote: Originally Posted by PatO

MS Paint? Are you on drugs?

I don't do drugs, but since you're such a nice and courteous guy why don't you redesign the scheme in a more evolved graphics package instead of throwing offensive remarks. This kinda behaviour will make me think at least twice before I will share any of my other projects. As they say no good deed goes unpunished.
FWIW I already had the main components in a png so it was a simple matter of copy & paste and some rearranging so no big deal.

Quote: Originally Posted by widower

You could also change the 2n3055 from a TO220 package to a TO3 package. It can handle larger currents without a heat sink. Better yet, the 3055 has a large on resistance, a FET would be able to handle a much bigger load without heating up because of the much lower on resistance.

the 2N3055 IS a TO3 package, the MJE3055 which I used is a TO220. of course the 2N3055 is way better, but I was a little constrained on space: it had to go in the lamp assembly which is kinda tight and the TO3 package is almost as big as the whole circuit

so for me the MJE3055 was the choice. anyway, to each his own... so if you have the space go for the 2N3055 by all means.

ethlar · 11-10-2005, 01:19 AM

my roomate at school and i are attempting to build this and have hit some issues. Im not a EE but he is, so he understands the electrical diagrams, he says there are a couple components that dont appear on the diagram, the resistor to the left of the pot, and the beige component in front of it. we built the circuit to spec based on the diagram as far as we could tell on a protoboard and hooked it up to a 12v supply and everything but couldnt get it to work. any troubleshooting suggestions?

PatO · 11-10-2005, 09:55 PM

Quote: Originally Posted by kronos

I don't do drugs, but since you're such a nice and courteous guy why don't you redesign the scheme in a more evolved graphics package instead of throwing offensive remarks. This kinda behaviour will make me think at least twice before I will share any of my other projects. As they say no good deed goes unpunished.
FWIW I already had the main components in a png so it was a simple matter of copy & paste and some rearranging so no big deal.

the 2N3055 IS a TO3 package, the MJE3055 which I used is a TO220. of course the 2N3055 is way better, but I was a little constrained on space: it had to go in the lamp assembly which is kinda tight and the TO3 package is almost as big as the whole circuit

so for me the MJE3055 was the choice. anyway, to each his own... so if you have the space go for the 2N3055 by all means.

I'm sorry if that remark was taken negatively. I meant it in a sarcastic tone to indicate that I admire your dedication to creating accurate and descriptive diagrams. Please don't think that I am bashing you in any way, shape, or form! I truly appreciate this diagram and will implement it as soon as time permits!

kronos · 11-12-2005, 07:19 PM

Quote: Originally Posted by ethlar

my roomate at school and i are attempting to build this and have hit some issues. Im not a EE but he is, so he understands the electrical diagrams, he says there are a couple components that dont appear on the diagram, the resistor to the left of the pot, and the beige component in front of it. we built the circuit to spec based on the diagram as far as we could tell on a protoboard and hooked it up to a 12v supply and everything but couldnt get it to work. any troubleshooting suggestions?

I have added two small resistors; 470ohm in series with SR1 and 1k2 in series with SR2 in order to have a small impedance when the pot's is zero so as the capacitors discharge or charge through some impedance instead of straight through wire (they're limiting the current a bit); they are not critical and as long as you don't set the pots to zero you don't have to worry. Indeed I added them after the scheme was done and I forgot to draw them in... my bad, but it should work without them given that they are a kind of... let's say added protection. check your connections on the protoboard, because my prototype was done without the small resistors as well and it worked from the moment I powered it up. what exactly is not working? does the led light when you power up the circuit? also take a multimeter and check voltage at:
pin 3: it should be aprox half the voltage of the source
pin 2: after power up it should raise from zero to aprox the voltage of pin 3 in somewhat less than the time constant for the SR1-C1 (time constant[seconds] = R [ohms] x C [farads])
tell me more details cause I'm troubleshooting blind here.
... ok, edited the first post with the updated scheme (the two resistors added)

Quote: Originally Posted by PatO

I'm sorry if that remark was taken negatively...

ok, no offense taken. I was tired and just had one of those days and everything upset me.

ethlar · 11-13-2005, 01:18 AM

thanks for the update. we were able to get the led to light but couldnt get the dome light, which i had removed from the car, to light up. we will get back into the electronics lab and check the voltages you listed. i will try to get more details after we get back in.

lez · 11-13-2005, 03:22 AM

Yeah I think you will find a small construction error, I have not built this but it looks like a working stable design to me.

(only reason I didnt build was my car has one of these in OEM)

Sparky928 · 03-28-2006, 06:55 PM

Kronos(or anyone else) what exactly is a 1k2 resistor? by process of elimination I see two 2.2K resistors, with 3 red bands, that are not mentioned on the diagram. Is that what you mean, 2.2K?

Vik · 03-31-2006, 09:47 AM

I am on Drugs......

Sweet Marihuana or hasjes, hmmmmmmmmm

But never again say something bad about ms paint. it's the best.....

Cheers

EU is the best

PatO · 04-01-2006, 10:17 PM

It's not MSPaint I have a problem with. It's spending so much time creating drawings with it. Of course, it could be said that spending a couple dozen hours per year fiddling with MSPaint would be better than spending a couple grand for Photoshop....
I'd rather pay the cash for PShop and spend the extra time hanging out with ViK...

disker · 09-21-2006, 11:20 PM

I was thinking - can't this just be accomplished by just a capacitor? The rest seems kinda unnecissary - but then again, I'm not an EE and only know enough about this stuff to get me in to some real trouble.

I'm sure that I'm probably way wrong, but if any light can be shed on why I'm worng, it would be appriciated because I do love to learn.

MANY thanks! I'll be building one of these hopefully this weekend when I put my new alarm system in.

Ciao!

Khurram · 11-13-2006, 06:06 AM

I constructed the entire circuit as per your supplied schematic, and matched it with the photo of the end product. when i tested it, it worked perfectly well, giving negative 12 volts dc in the bulb output terminal which stayed on before dimming off. problem is that it does not have enough current to light the bulb. although voltage across the output is 12 v, the current is only about 200 mA. why is this happening. the resistances i am usign are 470ohm, 100 ohm and 1.2k ohm. are they ok?

gr_diver · 07-28-2007, 04:42 AM

Hello friends of the forum! I am sorry to bring back an old topic.

I tried making the dimmer, from the schematic kronos kindly posted a while ago.

To begin with, I must say I have no idea about electronics. I am quite keen on electrics though, and assembling small circuits is not a problem. I assembled the dome dimmer, but I cannot get it to work.

One suspicion I have is that the parts shop did not have the LM258P, but gave me a LM358P as a substitution. Are these two interchangeable? I downloaded their datasheet, it is the same for both, but I couldn't understand if I can swap them...

Furthermore, I tried measuring the voltages at pins 2/3 of the IC. Pin 3 indeed has approximately half the voltage of the source. The voltage on pin 2 slowly increases and exceeds that of pin 3. In fact I am using a 9V battery for bench testing, and the voltage on pin 3 reaches 8V

. Pin 1 has no voltage, and this is why, I think, the LED does not get lit. If with the IC removed I momentarily short pins 1&2 on the soldered socket, the LED will flash.

Any help would be greatly appreciated. I am building this to install in my '78 car.

Thank you in advance!

gr_diver · 07-28-2007, 07:32 AM

Small update!

Stupid as it might seem, I had not connected pins 4 & 8 of the LM358 to + and - respectively. I said I am a complete amateur. Not on the schematic, not done

! But from the pictures i figured them out...

Now the circuit works, the LED lights when power is applied, then fades. Re-enganges if I ground the "door" lead and immediately fades if I connect the ACC lead to +.

BUT, it seems like it can't handle the current of a 10w bulb. I replaced the bulb with a led (with a resistor to feed it from +12V) and with it the circuit works nicely! But it can't work with the car's bulb... Seems like I have the same issue as Khurram.

gr_diver · 07-28-2007, 05:31 PM

Ok, I think I figured it out, after reading this article:

http://www.satcure-focus.com/tutor/page4.htm

I realized that the base did not receive enough current, to make the collector-emitter path "open" as needed, and allow sufficient current flow through. So I replaced R6 (39kΩ) with a 0-10kΩ potentiometer, and set just enough for the bulb to get fully lit during the delay stage. The potentiometer could go further than the point where the bulb reaches full brightness, but because of my ignorance on such operational things I decided to set it just enough.

I also used a small heatsink on MJE3055, because after fiddling with the circuit for about 10mins to set the delays to my liking, it had gotten hot. Now it gets just warm...

Thank you for your time!

pratikpawar · 10-08-2007, 11:54 AM

can you tell what is acc

where should i cannect it

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