# Help with this project circuit board! im new!

Discussion in 'The Projects Forum' started by Sweet06se, Jan 25, 2010.

1. ### Sweet06se Thread Starter Member

Jan 25, 2010
31
0
Hello all and as stated im new to this type of thing so please dont make fun!
I have this schamatic and im not sure how to read it and it is very confusing to me i have the parts to make it but i just dont understand!
is there somone that can make it alittle easier for me to read and more descriptive of what to do!

here is the schamatic

and then a completed pic NOT MINE!

2. ### Sweet06se Thread Starter Member

Jan 25, 2010
31
0
Please someone has to be able to help!!! <3<3

3. ### Wendy Moderator

Mar 24, 2008
21,437
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Have patience, it takes a while sometimes. reading the schematic I interpret it as something automotive, judging from the fog lamp labels.

The relays need individual designators. Putting designations on parts allows you to talk about them and describe their actions. Relay coil on the right is K1, Relay coil on the left is K2. Basically it is a set reset circuit, the two transistors keep the state steady, which way isn't important.

If TR1 is conducting then Q4 has ground on the gate, which turns Q4 off. The Drain of Q4 feeds a high to Q4, keeping it conduction. When K1 is energized C1, which has 0V charge, diverts the current from R4 through R3, turning TR1 off. This creates a feedback situation where Q4 turns on, which finishes turning TR1 off. C1 begins to charge to Vcc.

TR1 is off, Q4 is on. If K1 is toggled again the capacitor C1 dumps its charge through TR1, starting to turn TR1 on. Again, there is feedback, and the transistors flip states.

Basically a toggle type flip flop, using K1 as the clock.

If you want to figure currents start by making the assumption TR1 is off, and calculate from there. Then make the assumption TR1 is on, and calculate from there.

4. ### Sweet06se Thread Starter Member

Jan 25, 2010
31
0
again can anyone simplify it alil

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6. ### THE_RB AAC Fanatic!

Feb 11, 2008
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Each time you touch the "fog lamp switch" wire to ground, the output relay (on the right) will toggle, ie change state.

So if you connect a button to the input wire, each time you press the button the output relay will toggle on->off->on->off etc.

Which is what Bill said.

7. ### Sweet06se Thread Starter Member

Jan 25, 2010
31
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This is very helpfull thanks so much!

8. ### Sweet06se Thread Starter Member

Jan 25, 2010
31
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well ive tried to wire this up and i still cant get it....

does anyone have a bread board that they could wire it up and or just tell me the connection numbers?
and take a picture of it and or tell me conection spots?

9. ### Wendy Moderator

Mar 24, 2008
21,437
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Did you try installing it into a car, or are you trying it as a project? I would strongly recommend a breadboard for a first effort, to get things working.

If you are trying it as a breadboard then you will need a light bulb or LED/resistor on the output and a simple switch on the input.

10. ### Sweet06se Thread Starter Member

Jan 25, 2010
31
0

thanks for the responce.. no im trying this on a breadboard first.. and and using a switch and light as a tester but cant seem to wire it correctly

thats y i was asking if somone could assemble it and tell me the connections or numbers of lines they connected to on the breadboard.. ill give someone a couple bucks if they could do this for me!

11. ### Wendy Moderator

Mar 24, 2008
21,437
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I don't have a lot of free time. If you have a camera capable why not take a picture and post it?

This design is overkill. I think if I were to start from scratch I could do it with only the 2 relays. It is fundamentally a flip flop, nothing more.

I saw something similar using two 555s a while back, that used the same exact principle.

C1 is the memory of this circuit. Depending on whether it is charged or not causes the transistors to flip states, which causes C1 to change its state shortly after.

When I have a bit of free time I'll draw the complete circuit, including the switches and light bulb that is assumed to be there.

12. ### Sweet06se Thread Starter Member

Jan 25, 2010
31
0
wow i would realy appriciatte that!
the diagram only show 2 relays.. its just 2 mini 12v relay with 4 prongs in the picture it looks like 4 but accually 2..
yea that would be awesome if you could do that.. cause i seariously dont get this..

Thanks

Last edited: Feb 19, 2010
13. ### Sweet06se Thread Starter Member

Jan 25, 2010
31
0
anyone else care to help

14. ### Wendy Moderator

Mar 24, 2008
21,437
2,958
OK, here are the two missing components...

When the switch is pressed the light bulb will flip states (on/off or off/on).

I'll be back with other drawings. The relays as shown are slightly astandard, but they are pretty close to how such things are drawn. It is obvious to an experienced tech that there are only 2, with only one set of contacts.

Look at each transistor as an inverter, and follow what the cap does to the circuit when the switch is depressed. Keep in mind that the capacitor will either be fully charged or fully discharged. The two transistors are a classic set reset flip flop.

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15. ### Wendy Moderator

Mar 24, 2008
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Here is a simplified diagram...

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16. ### Sweet06se Thread Starter Member

Jan 25, 2010
31
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that looks much easier!
is that ll i need? where did all the other parts go? are they even needed?
what are those large arrows? but that makes much more sence now!
could you insert all the components into the picture?
here is what is said needed
- MPS2222A or similar small-signal NPN
1 - IRF510 n-channel MOSFET
1 - D1 1N4001 silicon diode
1 - R1 1M 0.25W
1 - R2 4.7M 0.25W
1 - R3 10k 0.25W
1 - R4 330k 0.25W
1 - C1 220nF ceramic disc, polyester or mylar film
1 - C2 100nF ceramic disc, polyester or mylar film
2 - 12v relays

17. ### Wendy Moderator

Mar 24, 2008
21,437
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A simplified diagram is meant to make things understandable, not generally meant to build. This one could be done, but if you want to light an LED it would need some changes.

You know, I've been so busy trying to explain the original circuit (which I thought was the point) it never occurred to me that you were trying to do something with it. What exactly are you trying to do?

This same circuit can be done with a simple single chip flip flop IC, with circuitry left over.

Why do you have to use those components (which doesn't include the 2N2222 transistor), is this a homework assignment?

Like I said before, both the transistors were wired as inverters. I was just showing you how they applied in the design.

Last edited: Feb 21, 2010
18. ### JoeJester AAC Fanatic!

Apr 26, 2005
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Would the OP state what their circuit is to do?

As it is now, with both relays identified as RLA, one can not determine when the contacts are changing state.

The circuit as drawn, even with two seperate relays (K1 and K2), the contacts to the fog light relay are supplying power to the fog light relay until one presses the switch. Then no matter what you do at the input (fog lamp switch), the output (fog light relay power) remained de-energized.

That is an unusual way to bias the first (leftmost) transistor.

19. ### Sweet06se Thread Starter Member

Jan 25, 2010
31
0
the purpose of the circut is as follows..

on a certian model car the foglights can only be turned on when the headlights are on..
so the purpose of the circut is to allow total control over the foglights allowing them to be turned on anytime wether the headlights are turned on or not... with the flip of a switch
the MPS2222A or similar small-signal NPN
was substituted with the br1 bc337 in the diagram but from what i was told i could use either..
hope this helps
so i doesnt neccesarlily need a tester just the final product that i could use in the car..

Last edited: Feb 22, 2010
20. ### Wendy Moderator

Mar 24, 2008
21,437
2,958
I understand what it is and how it works, but what I don't understand is what your assignment is. Are you trying to duplicate a preexisting circuit or design a new one from a standard set of parts, or something else altogether? You have an overabundance of parts for the job, but the way you stated the problem you have to use them all.

The key, like I said before, is using the capacitor as memory. Transistors and relays both make good logic modules, but the transistor can take a small charged/discharged capacitor and use it to control the rest of the circuit.

So what is the project, design something new, or breadboard an existing design, or something else?