Help figuring out this circuit

[predator0357]

Hello friends,
I need ur help figuring out what this and the parts and thats mark ones,
P.S
The IC is 555.
Freind of mine working in some place that have the circuit and every time that it doesnt work his boss get mad cuz it cost him like 145$ and looked it n found this ic 555 and told my friend that his boss get mogded, and told him to tell his boss that i can fix it for ½ the price and i told my friend how much the ic cost (0.05$)and he told me great go do it u got ur self a side job.

[stj]

Re: Help figuring out this circuit

other side of the board?

[chozo4]

Re: Help figuring out this circuit

The one circled green is your generic ceramic disc capacitor. It looks like either 102 (1000pf) or 103 (10000pf) from that view. The other one in red looks to be a variable resistor with the value 20468? Thinking off hand it might be a 200k adjustable resistor meant for loads up to a max of 68ma but I'm likely wrong there.

The small blue ball just under the edge of the green circle (unsure if that was also meant to be circled) would be a small inductor. Cannot tell the values in image however.

Though I'm tired and running on practically no sleep..
Observing the red/green LEDs, 555 with single inductor/capacitors in line with it I'm wagering it to be an adjustable charge circuit of sorts. Though it's missing the mosfet/transistor so might not be. No way to actually tell without seeing the bottom of the board as STJ states.

One thing I don't understand is the statement of 'everytime it doesn't work the boss gets mad'. Shouldn't they prototype it first before production to ensure it works at least in a basic capacity? Would save a lot of headache.

[selldoor]

Re: Help figuring out this circuit

If you dont know what these basic parts are it was rather foolish to say you can repair it for half the price. I really think we need to know what it is off

[stj]

Re: Help figuring out this circuit

whatever it is, it's junk.
the problem with analog oscillators is the time is not constant because the capacitors are effected by temperature and aging.
it may have been a valid design 20years ago,
but these days i would have just stuffed the whole circuit into an 8pin 50c microcontroller.

it's probably a pulse-stretcher btw,

[predator0357]

Re: Help figuring out this circuit

If you dont know what these basic parts are it was rather foolish to say you can repair it for half the price. I really think we need to know what it is off

FIRST I KNEW WHAT THOSE PARTS ARE!!!!
I know that small part is a cap i wasnt sure how to read it, and the second one in the red also i wasnt sure i knew its varible resistor (and my teacher said its a trimmer), and i said i can fix cuz 2 weeks ago in the class we did this exp.

[stj]

Re: Help figuring out this circuit

you read the trimmer like a surface mount resistor.
the first 2 digits are what you see, the 3rd digit is the number of zero's on the end.

so 204 = 200000 ohms or 200k

not much to go wrong other than the chip.

[mariushm]

Re: Help figuring out this circuit

The 555 chip is like a timer. There's pretty much 3 typical modes of operation for that chip, which you can read about here : http://www.555-timer-circuits.com/operating-modes.html

Take a piece of paper and draw the circuit on the piece of paper, then compare your design with the circuit for each of those typical three modes of operation.. you have examples at the link above, or you can search in google for "555 example circuits"

Probably even the 555 datasheets have example circuits in them - the fact that you came here to ask for help tells me you probably didn't even bother to search for information in the first place.

If the chip is running in a timer mode, you can use this page to figure out how
much time is the 555 supposed to be on, and how much time it's supposed to be off: http://www.555-timer-circuits.com/calculator.html

Then, you can compare expected results with what your board outputs and see if your 555 is faulty or not.

ps. What's up with that green led lead, it seems to be shorting that diode and resistor together. See if that's intentional.

[selldoor]

Re: Help figuring out this circuit

Probably even the 555 datasheets have example circuits in them - the fact that you came here to ask for help tells me you probably didn't even bother to search for information in the first place.

The OP is at school / college - I wonder if we are just doing his homework for him

[predator0357]

Re: Help figuring out this circuit

The OP is at school / college - I wonder if we are just doing his homework for him

Hehehehehehehehrh no its not my homework, homework i like very much do it on my own without help and geting mistakes and learn from them.

[predator0357]

Re: Help figuring out this circuit

The 555 chip is like a timer. There's pretty much 3 typical modes of operation for that chip, which you can read about here : http://www.555-timer-circuits.com/operating-modes.html

Take a piece of paper and draw the circuit on the piece of paper, then compare your design with the circuit for each of those typical three modes of operation.. you have examples at the link above, or you can search in google for "555 example circuits"

Probably even the 555 datasheets have example circuits in them - the fact that you came here to ask for help tells me you probably didn't even bother to search for information in the first place.

If the chip is running in a timer mode, you can use this page to figure out how
much time is the 555 supposed to be on, and how much time it's supposed to be off: http://www.555-timer-circuits.com/calculator.html

Then, you can compare expected results with what your board outputs and see if your 555 is faulty or not.

ps. What's up with that green led lead, it seems to be shorting that diode and resistor together. See if that's intentional.

Tnx 4 the help:-)
And yes this is the firsst thing that i notice with the led, look my sent this pic and to day i asked from him to pic more of this.
Anc again tnx 4 the help and understanding

[budm]

Re: Help figuring out this circuit

BTW, is this being used to control other board/circuits? The more info we have the better.

[predator0357]

Re: Help figuring out this circuit

Yes it controll a traffic Billboards that have on the same side 3 advertisement/Comercials and it control the time when the advertisement/Comercials turn to the second and the third and start over, the circuit working on 12[Vcc] DC( as i recall it turns every 8sec n when the 555IC doesnt work it wont turn and it happend when something jamming the billboard, not every time some time it just get fried:-) ).
Look this 555IC in this circuit is the weakes part, cap there is the second n third is resistors so as i see it, i want to build like 5 circuits like this one and add connector to the VCC+GND and when one of the billboard circuit get burned i will replace it with mine.
P.S
I knew its a 555 timer circuit but i love to hear others opinions cuz mayB some1 els see things that now i dont.

[stj]

Re: Help figuring out this circuit

it's pretty shit using a 555 in free-running mode for such a long time duration.

if you must use this design, you need lots of protection from spikes and shit.
input capacitors, input spike supression using a transorb,
output buffering through a transistor with a fuse on it.

if you want real advice,
post a schematic of the whole setup.
the psu, the motor and driver including what i assume is a camswitch with diodes across it etc.
actually a plain camswitch would have done it in the past.

[predator0357]

Re: Help figuring out this circuit

it's pretty shit using a 555 in free-running mode for such a long time duration.

if you must use this design, you need lots of protection from spikes and shit.
input capacitors, input spike supression using a transorb,
output buffering through a transistor with a fuse on it.

if you want real advice,
post a schematic of the whole setup.
the psu, the motor and driver including what i assume is a camswitch with diodes across it etc.
actually a plain camswitch would have done it in the past.

Hi,
Look i am not looking for new or better design, i am just looking for to remake this circuit to have spares for if one of the billboard get burned i will just come n replace the faulty circuit and then ill fix it

[stj]

Re: Help figuring out this circuit

then post a foto of the trackside of the board!

[budm]

Re: Help figuring out this circuit

You also need to remove that tape on the board so we can see verything, and we also need to know where those wires go to, it sounds like there is no transistor to drive the the load which may have exceed the 555 output drive capability.