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##### Projects Q/A / Re: 0v-30v power supply
« Last post by audioguru on August 22, 2014, 10:44:07 PM »
Here is a good 3A 0v-30v power supply.
It has a few serious problems, Kevin:
1) Its voltage gain is only 1 because the negative feedback is wrong.
2) Its slow output transistor will cause oscillation without compensation capacitors.
4) It will be destroyed if the output current is too high or is shorted because it is missing current limiting or regulation.

Here most problems are fixed except it still has no current limiting:
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##### Projects Q/A / 0v-30v power supply
« Last post by KevinIV on August 22, 2014, 09:34:17 PM »
Here is a good 3A 0v-30v power supply.
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##### Projects Q/A / Re: 0-30V Stabilized Power Supply
« Last post by audioguru on August 22, 2014, 09:03:05 AM »
Hello gurus,

I will build one of these.   I have a toroid transformer of 28V  3A.   So I think I need to run it with maximum of 2A, in order to not overload the transformer, right?  And in this case the only modification would be increasing R7 to 0.67 ohms/10W?  And whould I keep the 2x 2n3055,  or just one with big heatsink will do the job?

The 28V transformer produces a peak voltage of 39.6V. If the maximum output current from your project is 2A then the transformer must produce 39.6V x 2A= 79.2VA.
But the transformer is rated for 28V x 3A= 84VA so it will be very warm but be fine.

0.67 ohms is not a standard value, use 0.68 ohms for R7. Its max dissipation is 2 squared x 0.68 ohms= 2.72W. Use a 5W resistor.

The unregulated loaded voltage will be 39.6V - 2V - 1V= 36.6V. If the output is shorted at 2A then the output transistor (s) must dissipate 36.6V x 2A= 73.2W which is a lot for a single 2N3055 transistor even if it has a big heatsink but it will be fine if a fan is added. Use two output transistors on a pretty big heatsink without a fan.
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##### Projects Q/A / Re: 0-30V Stabilized Power Supply
« Last post by rvendrame on August 22, 2014, 08:50:06 AM »
Hello gurus,

I will build one of these.   I have a toroid transformer of 28V  3A.   So I think I need to run it with maximum of 2A, in order to not overload the transformer, right?  And in this case the only modification would be increasing R7 to 0.67 ohms/10W?  And whould I keep the 2x 2n3055,  or just one with big heatsink will do the job?

Thanks!
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##### Electronic Projects Design/Ideas / Arduino Based Remote Control Car Project
« Last post by dkwick on August 21, 2014, 01:10:56 PM »
Hi Friends,
I have built a Remote Controlled car using Arduino UNO, L298 based DC Motor driver circuit and Two Gear Motors. I have created a step by step tutorial to create this project  . I would like to share my project details with you  .

Project URL - http://www.manelsoft.com/projects/arduino_rc_car.aspx

Please see the attached images of the final version.
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##### Microelectronics / Re: USART interrupt ATMega168
« Last post by liquibyte on August 21, 2014, 10:58:32 AM »
Have you tried an AVR forum?  I suspect the difference from working to not will be in the differences between the chips themselves.
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##### Electronic Projects Design/Ideas / Bipolar LED Driver Circuit
« Last post by sudheerelktronics on August 21, 2014, 06:14:29 AM »
Here is a simple bipolar LED driver circuit in which we use a microcontroller to drive the bipolar LED. The LED used here has a forward voltage drop of 2.2V and hence can be biased using a 5V supply. The control is done by the microcontroller program, based on the inputs given from two push buttons.

Bipolar LED Driver Circuit Diagram:

It is a simple circuit and the design mainly involves designing the interfacing of Microcontroller, designing the oscillator and reset circuits for the microcontroller and selection of the LED resistor.

The microcontroller interfacing is accomplished by connecting two push button switches to port P1 and connecting the two terminals of bi color LED to port P2.

Bipolar LED Driver Applications:
• This circuit can be used for indication purposes.
This circuit can be used at applications where flashing of light is required, as in beacon flashing.

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##### Microelectronics / USART interrupt ATMega168
« Last post by thebignoob on August 21, 2014, 03:25:42 AM »
Hello,
I was using USART interrupts to handle data transfer from PC to uC so that I could send that data to another remote PC using nRF24L01. Everything worked just fine with ATMega88, but on one side i had to switch to ATMega168 and then... everything stop working ...
So I tried to debug it... one thing at the time...

USART communication is working when I send some data from PC to uC and back... But when i try to do that using USART interrupt problem occurs... When I enter any character from terminal it goes crazy .... starts printing some symbols and blinking dash goes left to right all the time (pretty fast)... I go back again to ATMega88 and everything works...

Usart init and 2 functions that i used for communication ....
Code: [Select]
`void usart_init(void){        unsigned int USART_BAUDRATE = 9600; unsigned int ubrr = (((F_CPU / (USART_BAUDRATE * 16UL))) - 1); UBRR0H = (unsigned char)(ubrr>>8); UBRR0L = (unsigned char)ubrr; UCSR0B = (1<<RXEN0)|(1<<TXEN0);  UCSR0C = (1<<USBS0)|(3<<UCSZ00);}void usart_transmit(uint8_t data){ while ( !( UCSR0A & (1<<UDRE0)) ); UDR0 = data;}uint8_t usart_receive( void ){ return UDR0; }`

Enable usart interrupt
Code: [Select]
`UCSR0B |= (1<<RXCIE0);`
ISR
Code: [Select]
`ISR(USART_RX_vect){ uint8_t W_buffer[8]; int i; for (i=0;i<8;i++) { W_buffer[i]=usart_receive(); usart_transmit(W_buffer[i]); } usart_transmit('#');  }`I tried printing something at the beginning of the ISR to see if it goes inside but that never happens.
Anyone have a idea what could be the issue here ? I feel i just go round and round in circles....
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##### Electronic Projects Design/Ideas / Re: Building an amplifier
« Last post by audioguru on August 20, 2014, 07:08:24 PM »
I looked up the data sheet but it's a little difficult for me to figure out the schematic. I think the box in the middle must be the ic because the pins are listed on the outside of it. Is the circuit inside of the box the circuitry inside the ic ir is that part of what needs to be put together?
Since you do not understand the extremely simple schematic then maybe you should buy an amplifier that is already made.

Quote
I guess the reason for me asking about the ics again is just to get ideas of more ics that might work so I can have more of a variety to pick from.
You were given 3 choices. Narrow down how much power, what supply voltage??
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##### Electronic Projects Design/Ideas / Re: Building an amplifier
« Last post by liquibyte on August 20, 2014, 08:17:50 AM »
Also I just looked at the amp on newark and the page with the item says they charge a \$20 freight charge per order. Is that something I would have to pay or is it some kind of complicated thing that I don't understand?
Also, Mouser and Digikey.  Since we don't know where you're at, shipping will vary based on that.  I'm in MA right now and have ordered stuff from both of these and shipping is under \$10 for a low weight order.  Having said that, it's cheaper to over order with the added benefit of having stock on hand for next time.  For passive assortments use Ebay (trick is US only, free shipping) unless you need something special.  I don't use Newark because their website was coded by idiots.
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