[SOLVED] Tip41c/42c arrangement problem

[Javid.zare.s]

hi, im rebuilding a dc to ac converter which I was able to build last year
after that I just disassembled everything from project board. now I'm trying to build that same design but It's just making short circuit!
I think that it might be the arrangement of two transistors, this is the schematics:
**broken link removed**
inverter circuit:
**broken link removed**
my build:
**broken link removed**

tip42 pin 1 to pin 1 of tip41
tip42 pin 2 to pin 3 of tip41
tip42 pin 3 to gnd
tip41 pin 1 to pin of tip42
tip41 pin 2 to vcc
tip41 pin 3 to pin 2 of tip42
according to datasheets I should be fine but I tried many arrangements with no success

 

[betwixt]

Horrible circuit, even worse construction.
It looks like there are solder shorts everywhere and even if there wasn't, how are you going to fit the heat sink to the transistors.

Brian.

 

[Javid.zare.s]

Horrible circuit, even worse construction.
It looks like there are solder shorts everywhere and even if there wasn't, how are you going to fit the heat sink to the transistors.

Brian.

LoL, I wasn't expecting much heat from it so there's not much space for cooling department.
but beside all terrible soldering and stuff... is the transistors wired right?(legs are not shorted for surw)

 

[betwixt]

It isn't easy to see but I think it's right. There is more to it than just joining the right places though, you need to be sure the voltage at the NE555 isn't varying as the transistors draw current, ideally by using a ground plane to ensure the potential between ground points is as low as possible. The wiring around the timing components should also be short or they will pick up switching currents. Seriously though, that circuit is never going to work well, with relatively small changes it can be made to work much better.

How much power do you expect it to produce? I would guess it is only capable of < 5W.

Brian.

 

[Javid.zare.s]

It isn't easy to see but I think it's right. There is more to it than just joining the right places though, you need to be sure the voltage at the NE555 isn't varying as the transistors draw current, ideally by using a ground plane to ensure the potential between ground points is as low as possible. The wiring around the timing components should also be short or they will pick up switching currents. Seriously though, that circuit is never going to work well, with relatively small changes it can be made to work much better.

How much power do you expect it to produce? I would guess it is only capable of < 5W.

Brian.

what? 5 watt only? no I was thinking about at least 20watts
I wanna use it for our camping where we need to charge flashlights and cell phones
so there will be at least 2 devices charging at the same time...
I saw this schematics and thought to build it, so I ordered all stuff for it
I will remember to check voltage at 555, another question :
lets say power source is a 14v battery, will using a 7812(12v regulator) before ne555 help for more stable voltage?

 

[betwixt]

If you assume maybe 30% efficiency then 70% of the power is lost as heat.
If that 30% gave you 20W, around 45W would be given off as heat. The current consumption would be about 4A from 12V.

It would be FAR more efficient to drop the 14V down directly to the voltage needed to charge the flashlight and phones, you could achieve >95% efficiency easily without also having to carry a heavy transformer around with you.

Answering your question though, yes regulating to 12V would be a good idea but bear in mind that a 7812 needs around 15V at its input to regulate properly. You could use a low drop out regulator but as soon as the source dropped to maybe 13V it would still stop working. More important is that the wiring will drop some voltage because of the current flowing through it. That means the voltage at each end of the same wire will be slightly different, maybe not by much but enough that the circuit misbehaves. You have to be very careful to ensure the oscillator side (the NE555) gets a clean supply or the output stage may oscillate as well!

Brian.

 

[Audioguru]

Where is the schematic? The attachments do not work.

 

[Javid.zare.s]

If you assume maybe 30% efficiency then 70% of the power is lost as heat.
If that 30% gave you 20W, around 45W would be given off as heat. The current consumption would be about 4A from 12V.

It would be FAR more efficient to drop the 14V down directly to the voltage needed to charge the flashlight and phones, you could achieve >95% efficiency easily without also having to carry a heavy transformer around with you.

Answering your question though, yes regulating to 12V would be a good idea but bear in mind that a 7812 needs around 15V at its input to regulate properly. You could use a low drop out regulator but as soon as the source dropped to maybe 13V it would still stop working. More important is that the wiring will drop some voltage because of the current flowing through it. That means the voltage at each end of the same wire will be slightly different, maybe not by much but enough that the circuit misbehaves. You have to be very careful to ensure the oscillator side (the NE555) gets a clean supply or the output stage may oscillate as well!

Brian.

hi again, I've desoldered everything and rearranged them on project board, circuit works ,i used a transformer which gives 120volt ac at output.
there's no thermal issue until I connect a load which is a tiny 9v adaptor (5w) for a short time, the transistors are just fine but the 555 gets enormously hot,
The circuit or ic didn't damage cause I disconnected the power, I was expecting heat from transistors but the 555?thats odd

Where is the schematic? The attachments do not work.

there it is:

but can you help me with the last post? everything is fine but heat from 555 is not normal
power source is a car battery 12.7v (~70amp)

 

[Audioguru]

What is the part number of the 555? If it is from China then it is probably a fake.

Maybe you connected the polarity of the battery backwards?
Even if you connected the transistors completely wrong so they are a dead short, the 555 is able to drive the 100 ohms resistor and not get very hot but maybe just get fairly warm. The resistor will get hot.

That circuit has so many voltage losses that it Does Not Work:
1) The output of the 555 goes from +2V to +10V if it has a 12v supply.
2) Then the output of the 100 ohms resistor goes from about +6V to +8V.
3) The output of the transistors will go from about +7V to +7V so the output is Zero.
4) The output capacitor also has some voltage loss.
5) The inductor L1 also has some voltage loss.

The horrible schematic shows a simple AC transformer. Then why did you use a DC adapter that is completely different?

 

[Easy peasy]

TIP41A 42A has fairly low current gain - so you are asking a lot to drive it direct from a 555 ( esp a CMOS one ) - this is one of those ckt's that is not that flash ...

 

[Javid.zare.s]

What is the part number of the 555? If it is from China then it is probably a fake.

Maybe you connected the polarity of the battery backwards?
Even if you connected the transistors completely wrong so they are a dead short, the 555 is able to drive the 100 ohms resistor and not get very hot but maybe just get fairly warm. The resistor will get hot.

That circuit has so many voltage losses that it Does Not Work:
1) The output of the 555 goes from +2V to +10V if it has a 12v supply.
2) Then the output of the 100 ohms resistor goes from about +6V to +8V.
3) The output of the transistors will go from about +7V to +7V so the output is Zero.
4) The output capacitor also has some voltage loss.
5) The inductor L1 also has some voltage loss.

The horrible schematic shows a simple AC transformer. Then why did you use a DC adapter that is completely different?

this circuit is supposed to be used with a solar panel when camping, the output of it is regular ac to charge different devices such as flashlights phones etc, thats the load (adapter) that im talking about.
the circuit is now resoldered and works with 120volt ac at output , but when I connect a load the timer ic gets super hot in seconds(but still functions)
I was expecting heat from transistors and not the timer, how to solve this?

the ic itself is definitely made by Chinese but is functioning well in any circuit and I had no issues
- - - Updated - - -

TIP41A 42A has fairly low current gain - so you are asking a lot to drive it direct from a 555 ( esp a CMOS one ) - this is one of those ckt's that is not that flash ...

so is there any suggestions ? I'm getting tired of blowing up timer ICs, what can I do about it? will a capacitor at output of timer make any difference?

 

[andre_luis]

I was expecting heat from transistors and not the timer, how to solve this?

Me too, so review the above messy assembly, or better, get rid of that and make another one few more carefully. You are wasting your and others time with something notoriously prone of giving headache. If you are not familiar with welding, consider using a breadboard.

 

[betwixt]

A question before moving on: that transformer you are using, does it have a center tap? In other words is it a 12V to 230V type with two primary wires and two secondary wires or does it have 12-0-12 to 230V windings.

If it is center tapped (12-0-12) it is much easier to make an efficient inverter with a simple circuit.

Brian.

 

[Audioguru]

How can the timer IC get hot when its output feeds fairly low current into the 100 ohms resistor, not into the load?
The 555 would get hot if its output is shorted, but instead it feeds a 100 ohms resistor.
If the resistor is shorted to ground or to the 12V supply then its output current would be 10V/100 ohms= 100mA.
Then its heating would be (12V - 10V) x 100mA= 0.2W but for only half the time since it rests for the halftime it does not drive the short so its total heating is 0.1W.
Its datasheet shows that its maximum allowed heating (dissipation) is 1.18W so it gets warm at only 0.1W, not hot.

Check your wiring to make certain the pin 3 output of the 555 feeds the 100 ohms resistor with no short circuit.
Measure the 100 ohms resistor to be certain it is not 10 ohms or 1 ohm.

 

[andre_luis]

so is there any suggestions ?

I would start by answering the questions:

What is the part number of the 555?

There are variants of the 555, some of them (actually, few manufacturers) with limited supply voltage, slightly below what would be expected from a charged battery, particularly during charging, if with a low quality charger which can easily reach far beyond 14v.

power source is a car battery 12.7v (~70amp)

Just to check: Are you using any fuse? Not that the lack of one could explain the heating due to some previous misconnection, even because in this case, without protection one would expected the circuit got into combustion, nothing quite different from the aspect of the above assembly. Was there any incident worthy to be mentioned ?

 

[Easy peasy]

you need to find xtors with much higher gain ...

 

[Javid.zare.s]

Me too, so review the above messy assembly, or better, get rid of that and make another one few more carefully. You are wasting your and others time with something notoriously prone of giving headache. If you are not familiar with welding, consider using a breadboard.

in my last post i said i reassembled everything and attached them on project board for now , so forget about that messy welding . everything works well before connecting a load which generates heat in ne555 chip.(output still works fine, ne555 is hot to touch)

A question before moving on: that transformer you are using, does it have a center tap? In other words is it a 12V to 230V type with two primary wires and two secondary wires or does it have 12-0-12 to 230V windings.

If it is center tapped (12-0-12) it is much easier to make an efficient inverter with a simple circuit.

Brian.

yes it is. two wires for primary and three of them are secondary which gives me three different options in output (~120v-~340v~90v)

How can the timer IC get hot when its output feeds fairly low current into the 100 ohms resistor, not into the load?
The 555 would get hot if its output is shorted, but instead it feeds a 100 ohms resistor.
If the resistor is shorted to ground or to the 12V supply then its output current would be 10V/100 ohms= 100mA.
Then its heating would be (12V - 10V) x 100mA= 0.2W but for only half the time since it rests for the halftime it does not drive the short so its total heating is 0.1W.
Its datasheet shows that its maximum allowed heating (dissipation) is 1.18W so it gets warm at only 0.1W, not hot.

Check your wiring to make certain the pin 3 output of the 555 feeds the 100 ohms resistor with no short circuit.
Measure the 100 ohms resistor to be certain it is not 10 ohms or 1 ohm.

if your calculations are true then that will be resolved by a heatsink and fan?
im certain that what ive built is exactly same as schematics but ok ill do the measuring again asap .
can i for example connect the pin 3 of the ne555 to another hi-power pnp transistor then conect the output of that transistor to base of tip41\42? will it work?

I would start by answering the questions:



There are variants of the 555, some of them (actually, few manufacturers) with limited supply voltage, slightly below what would be expected from a charged battery, particularly during charging, if with a low quality charger which can easily reach far beyond 14v.



Just to check: Are you using any fuse? Not that the lack of one could explain the heating due to some previous misconnection, even because in this case, without protection one would expected the circuit got into combustion, nothing quite different from the aspect of the above assembly. Was there any incident worthy to be mentioned ?

its written "NE555P 93M DN1519"
NO the circuit is not fused. circuit is working ok without load ,120v ac with no issues. as soon as the load kicks in the heat goes up

you need to find xtors with much higher gain ...

i have no idea what the xtors is ! can i do what i explain in above sentence? adding a pnp transistor with higher gain at pin 3 of NE555 ic then connect output of it to base of tip41\42?
idont know much about electronics or these stuff its not the field of my education, so excuse me if it sounds funny

 

[andre_luis]

everything works well before connecting a load which generates heat in ne555 chip.(output still works fine, ne555 is hot to touch)

According to the schematic you have attached at post #8, this is not the same connection.

tip42 pin 2 to pin 3 of tip41

It would be expected both pin 3 connected together, review TIP41/42 datasheet.
By the way, Emitter for both NPN and PNP variants is at pin 3.

 

[Audioguru]

It is impossible for an NE555 to get hot in that circuit since it is driving only 100mA into a 100 ohms resistor. Then why do you need a heatsink and fan? Why add another transistor? Fix the problem instead:
1) Is the power supply voltage 15V or less?
2) Is the IC with its pins backwards? There is a dimple on the case near its pin 1. Then the pins count counter-clockwise.
3) Are the pins on the transistors connected correctly?

 

[Javid.zare.s]

It is impossible for an NE555 to get hot in that circuit since it is driving only 100mA into a 100 ohms resistor. Then why do you need a heatsink and fan? Why add another transistor? Fix the problem instead:
1) Is the power supply voltage 15V or less?
2) Is the IC with its pins backwards? There is a dimple on the case near its pin 1. Then the pins count counter-clockwise.
3) Are the pins on the transistors connected correctly?

1)exactly 13.7 v to be accurate
2)timer pins order is right and circuit operating at 120volt at output
3)yes they are
-I have no idea for that heat, maybe the timer chip is faulty and I need to replace it