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Binary 1011001101
Nobel Prize Winner
United Kingdom
569 Posts |
 Posted - Sep 18 2006 : 2:54:59 PM
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| What is cheaper buying a 300W inverter of making one? i have seeen them on sale for crazy prices. |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Sep 18 2006 : 7:03:29 PM
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| I have seen very inexpensive Chinese inverters. They cost less than the freight. I don't know if they are any good and how long they would last. |
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Binary 1011001101
Nobel Prize Winner
United Kingdom
569 Posts |
Posted - Sep 19 2006 : 12:08:27 PM
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| i am guessing ebay... |
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mathbob
New Member
2 Posts |
Posted - Sep 22 2006 : 11:58:31 AM
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| Here's a new twist. I need a simple - and cheap - way to ring a phone on stage. Needed: 50-100V, 20-50 mA or so, at 20 (yes 20) Hertz. Tis little nveter looks like it could do the trick. What values ahould the time constant have to do the 20 cycles (20-30 OK)? I'd like to run it from a 9V battery. With such low power, I'm not expecting anything to blow. Thanks! |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Sep 22 2006 : 7:54:06 PM
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This project has errors that cause it to waste a lot of battery power to blow up its capacitors and get hot. A little 9V battery would power it for only a few minutes before it is dead.
There are good oscillator circuits on the web designed to ring a phone. |
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mathbob
New Member
2 Posts |
Posted - Sep 23 2006 : 07:33:57 AM
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"There are good oscillator circuits on the web designed to ring a phone."
Could you direct me to one? Thanks! |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
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Benito
Apprentece
5 Posts |
Posted - Sep 27 2006 : 2:42:24 PM
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quote:
Originally posted by audioguru
A square-wave inverter is about 83% efficient so a 5000W inverter would heat with 1000W. If the battery is only 12V then the current would be a whopping 500A! A car battery would explode! 5 big car batteries in parallel would run the inverter for only 1 hour before their charge is gone.
Rediculous.
Is there a formula or table that can be used to guide the tinkerer to switch the parts neccessary to get more power out in proportion to the small power in? |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Sep 27 2006 : 7:46:14 PM
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quote:
Originally posted by Benito
Is there a formula or table that can be used to guide the tinkerer to switch the parts neccessary to get more power out in proportion to the small power in?
An electronic circuit cannot make power!
Power out must be less than power in because of losses that cause heating. |
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Benito
Apprentece
5 Posts |
Posted - Sep 28 2006 : 1:45:40 PM
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quote:
Originally posted by audioguru
An electronic circuit cannot make power!
Power out must be less than power in because of losses that cause heating.
I understand that power must come from some where before the circuit, as designed, can alter that power.
Why asked for a table or formula?
1. I am an amateur in electronics and definitely want to learn.
2. I would like to become skilled at calculating how many amps will come out of the circuit along with the 110V at 60 Hz when the source of the power is a 12V battery. Would also like to figure out which parts to replace in order for the circuit to handle 2 or more 12V batteries in series for more power or parallel for higher input voltage.
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Sep 28 2006 : 8:32:08 PM
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quote:
Originally posted by Benito
I would like to become skilled at calculating how many amps will come out of the circuit along with the 110V at 60 Hz when the source of the power is a 12V battery.
Power= Volts x Amps. 12V (battery)x 500A (rediculously high current)= 6000 Watts into the inverter. The inverter circuit isn't perfect so heats with 1000 Watts. Therefore the total output power is 5000 Watts which is 120V at 41.67A.
quote:
Would also like to figure out which parts to replace in order for the circuit to handle 2 or more 12V batteries in series for more power or parallel for higher input voltage.
In series the batteries double the voltage, in parallel they double the current. The inverter circuit and its load determine the amount of output power if the batteries can supply it.
The text in this project is wrong. It doesn't give more power just by using more powerful transistors or transformer. This project doesn't work anyway.
A properly designed inverter has a max output power. Increasing its output power is a complete re-design. |
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Benito
Apprentece
5 Posts |
Posted - Sep 29 2006 : 06:19:41 AM
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quote:
Power= Volts x Amps. 12V (battery)x 500A (rediculously high current)= 6000 Watts into the inverter. The inverter circuit isn't perfect so heats with 1000 Watts. Therefore the total output power is 5000 Watts which is 120V at 41.67A.
Nice! The voltage was increased by a factor of 10, and the amps reduced by a factor of approximately 12. Therefore, 12V x 60A = 720W. The output is then 120V x 5A = 600W. Got it!
quote:
In series the batteries double the voltage, in parallel they double the current. The inverter circuit and its load determine the amount of output power if the batteries can supply it.
Batteries in series, the voltage is added. In parallel, the amp is added. Got it!
quote:
The text in this project is wrong. It doesn't give more power just by using more powerful transistors or transformer. This project doesn't work anyway.
Only the simplicity of the schematic attracted me to the forum and increased my desire to learn how it works, and then put one together. I took a look at the 500W schematic you provided a link for and it does not look simple or easy to build by some one like me. So, at the moment I need help with the calculation on how much to put in, what is going to happen to that, what is the role of each component, what comes out, etc.
1. Now, what does the amp rating of the transformer do to the current? (I presumed it is something basic, right?)
2. Is this correct? Two 12V 60A batteries in parallel = 12V x 120A = 1,440W. The output is then 120V x 10A = 1,200W
Thank you, audioguru, and please patiently continue helping. I am looking forward to be a great apprentice to/with all of you mentors.
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Edited by - Benito on Sep 29 2006 08:54:43 AM |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Sep 29 2006 : 09:25:12 AM
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The 500W inverter that I helped fix uses many cheap power transistors that are available in The Philippines where it is used a lot. The transistors could be replaced by fewer power Mosfets in a slightly different design if they are available.
A transformer for a 500W inverter needs a 50A low voltage winding (600W from 12V battery, 100W wasted as heat = 500w output)so it would probably need to be custom-made. |
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tim
Mad Scientist
198 Posts |
Posted - Oct 02 2006 : 9:24:02 PM
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| HEY GUYS, ANYONE OUT THERE HAVE ANY USEFUL CIRCUITS FOR THE CAMERA FLASH CIRCUIT. ALREADY MADE A FAST STROBE. THERES GOT TO BE SOME USE FOR A CIRCUIT THAT MAKES 325 VOLTS. |
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sbresani
New Member
3 Posts |
Posted - Oct 05 2006 : 09:36:15 AM
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| hey, im doing a project for school and doing the dc/ac inverter, but is there a way that instead of getting an output of 120v i can get 24v? |
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Topic |
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12/120V inverter again
