my teacher once said that minus ( - ) is the same as ground
then I suggest that your teacher reads up on split-rail power supplies
minus (-) on a schematic is a reference , just like +ve , -ve , vcc , vss etc... they have specific meanings within the context of the circuit in question.
ground , earth etc *may* be connected to the mains earth or ground ( and generally are ) but you should check the schematic to be sure.
you cannot arbitrarily connect a 'ground' or '-' point to mains earth and expect to be safe without a good understanding of the circuit.
on a split rail PSU there are generally 3 "output" points :
1) + , vcc , +ve or similar
2) ground , gnd , 0 , or similar
3) - , vss, -ve or similar
depending on the circuit the 'ground' or '0' *may* be connected somehow to mains earth , usually it is not, at least not directly.
you certainly cannot assume that the '-' would be connected.
there are some points which definately *should* be connected to mains earth - metal casework for example.
Don't connect anything to any part of the mains unless you are absolutely sure what you are doing
you are not a cat , you have just the one life.
ray
then I suggest that your teacher reads up on split-rail power supplies
minus (-) on a schematic is a reference , just like +ve , -ve , vcc , vss etc... they have specific meanings within the context of the circuit in question.
ground , earth etc *may* be connected to the mains earth or ground ( and generally are ) but you should check the schematic to be sure.
you cannot arbitrarily connect a 'ground' or '-' point to mains earth and expect to be safe without a good understanding of the circuit.
on a split rail PSU there are generally 3 "output" points :
1) + , vcc , +ve or similar
2) ground , gnd , 0 , or similar
3) - , vss, -ve or similar
depending on the circuit the 'ground' or '0' *may* be connected somehow to mains earth , usually it is not, at least not directly.
you certainly cannot assume that the '-' would be connected.
there are some points which definately *should* be connected to mains earth - metal casework for example.
Don't connect anything to any part of the mains unless you are absolutely sure what you are doing
you are not a cat , you have just the one life.
ray
If you have no mains earth, then obviously you can't connect to it.
Check your circuit schematic , it will show you what the local 'ground' will be.
I would personally be wary of using ungrounded main connections unless I was sure that there was no possibility of coming into contact with any live connections.
a proper understanding of the circuit is required before any connection to mains circuitry is attempted. I cant really give any better advice than this
Check your circuit schematic , it will show you what the local 'ground' will be.
I would personally be wary of using ungrounded main connections unless I was sure that there was no possibility of coming into contact with any live connections.
a proper understanding of the circuit is required before any connection to mains circuitry is attempted. I cant really give any better advice than this
I never have worked on live equitment. I accept that in some cases that you have to do this.
Am right in thinking that if you turn of the power and short the caps this will protect you from any electrical shocks or do they have other places to hide in the circuitry.
My mum is very very sencitive/conuctive she gets static shocks off almost anthing metal(lift buttons, car, unpainted fridge and so on)
can any body think why this is. i have never had this problem I once got an electric shock of an english 240v socket when i was first at school the only thing that happend was that my thum felt like somone had fliked the nail hard. why did it not hurt me when i got a mains shock but it hurts my mum when she gets static shocks.????????????
Am right in thinking that if you turn of the power and short the caps this will protect you from any electrical shocks or do they have other places to hide in the circuitry.
My mum is very very sencitive/conuctive she gets static shocks off almost anthing metal(lift buttons, car, unpainted fridge and so on)
can any body think why this is. i have never had this problem I once got an electric shock of an english 240v socket when i was first at school the only thing that happend was that my thum felt like somone had fliked the nail hard. why did it not hurt me when i got a mains shock but it hurts my mum when she gets static shocks.????????????
It's dependant of many factors: humidity, dampness of the skin, gender, electrolyte levels in the body and so on... There's no real clear cut answer. You must also remember that static electricity is measured in kV so while it has very little current, it certainly has the ability to give a nasty sting. On the other hand, you were indeed a lucky man to receive a 240VAC shock with such minor side effects.
Olle, if you explain to the guys here what you are going to do, it's much easier for them to know what they should answer you.
You can put "plus" to ground like old brittish cars but if you want to connect stuff it may not be wise
Very often you don't need to ground your circuits at all (just to shield or connect to chassis), I mean "skyddsjorda", connect to protective earth, it depends...
You can put "plus" to ground like old brittish cars but if you want to connect stuff it may not be wise
Very often you don't need to ground your circuits at all (just to shield or connect to chassis), I mean "skyddsjorda", connect to protective earth, it depends...
You can put "plus" to ground like old brittish cars but if you want to connect stuff it may not be wise
Argghhhh ! , don't remind me.....
how can you make a power supply that is not a split-rail power supply?
well, a single rail supply would qualify , that is a supply which only has one output ( could be positive or negative ) for example a 12volt car battery charger is a simple single rail supply.
A split-rail supply is usually characterised by a positive and a negative rail ( usually symetrical e.g +45v and -45v , or +15v, -15v ).
In both cases the 'ground' from the power supply is simply a reference point from which the voltage rails are measured. you can think of it as the current return if you like.
the simplest power supply example I can think of is a battery. The +ve is the power rail, the -ve is the 'ground' or return if you will.
This is a 'single rail' power supply.
If you connected two batteries in series, you could have a +ve, a ground or 0v where the two batteries connect, and a -ve from the tail end of the 'lower' battery. If you connected a voltmeter to the 'ground' you would measure a positive voltage on the +ve and a negative on the -ve.
obviously you don't need to connect the 'ground' of your battery(s) to the mains earth , any more than you particularly need to connect the 0v 'ground' of your power supply.
remember that the '0v' or 'ground' from your power supply is the reference from which all voltages in the circuit are measured, unless otherwise stated.
ray
Argghhhh ! , don't remind me.....
how can you make a power supply that is not a split-rail power supply?
well, a single rail supply would qualify , that is a supply which only has one output ( could be positive or negative ) for example a 12volt car battery charger is a simple single rail supply.
A split-rail supply is usually characterised by a positive and a negative rail ( usually symetrical e.g +45v and -45v , or +15v, -15v ).
In both cases the 'ground' from the power supply is simply a reference point from which the voltage rails are measured. you can think of it as the current return if you like.
the simplest power supply example I can think of is a battery. The +ve is the power rail, the -ve is the 'ground' or return if you will.
This is a 'single rail' power supply.
If you connected two batteries in series, you could have a +ve, a ground or 0v where the two batteries connect, and a -ve from the tail end of the 'lower' battery. If you connected a voltmeter to the 'ground' you would measure a positive voltage on the +ve and a negative on the -ve.
obviously you don't need to connect the 'ground' of your battery(s) to the mains earth , any more than you particularly need to connect the 0v 'ground' of your power supply.
remember that the '0v' or 'ground' from your power supply is the reference from which all voltages in the circuit are measured, unless otherwise stated.
ray
Olle has troubles to really ask the right question (only 16) but he has explained a little bit more in swedish here .
The question is really simple: 230 VAC ????? +-30 V or so. He plan to use TDA2050. What does he need in between?
BTW: www.diyforum.net is OK forum in Sweden but it's a difference between 200 users and 4000 users at www.diyaudio.com. Still, a few people there have something to give.
I want also to wish young Olle good luck with his (first?) project.
The question is really simple: 230 VAC ????? +-30 V or so. He plan to use TDA2050. What does he need in between?
BTW: www.diyforum.net is OK forum in Sweden but it's a difference between 200 users and 4000 users at www.diyaudio.com. Still, a few people there have something to give.
I want also to wish young Olle good luck with his (first?) project.
acctuallly that wasnt really what i was asking for, but ... i needed to understand it to know what i needed. and there is something about my mind that makes it go crazy if it doesnt understand everything(really enoying actually, i cant just let go of things).
I think my problem was that i had it all mixed up from the start
yes, this is my first project if you dont count some speakers i built.
you have all been very helpful and finaly ive understood
I think my problem was that i had it all mixed up from the start
yes, this is my first project if you dont count some speakers i built.
you have all been very helpful and finaly ive understood
You can learn a lot simply by looking at schematics of amplifiers and their power supplies.
Check also Rod Elliott's stuff. I would also recommend headwize and their DIY and Project section.
Check also Rod Elliott's stuff. I would also recommend headwize and their DIY and Project section.
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