Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Issue with power supply

Status
Not open for further replies.
V

venkates2218

Full Member level 6
Joined
Sep 30, 2016
Messages
354
Helped
1
Reputation
2
Reaction score
1
Trophy points
1,298
Activity points
4,306
POWER ISSUE.png
1.POWER 1 for external supply.

Friends,I created an alarm system for my factory.The concept of the project is,when I pressed the button the horn will blow.The horn will blow in two types.
1.Blows continuously.
2.Blow with small interval time(Like LED blinking).

For power supply I used an battery.Because it will work under UPS connection.
1.My problem is when I connected all power point in circuit to UPS means,It hanging down.I checked the voltage across the PIC'S VSS and VDD,RESET pins their is 4.5V across it.But I dono whats the problem is..
2.I tried with another one supply.For PIC operation I used an 12V adapter and power supply from battery is connected to horn through realy to control it.At this condition it working fine.

When I tried to operate all with battery supply means it hanging down.
I dono whats the probelm with this circuit.

My requirement is I need to operate everything in battery supply only.
So please help to find out the problem in this circuit.
 

Why don't you use internal RC oscillator ? If your application does not require high speed it is better to use internal clock.
Have you taken a separate track for your relay transistor ground ? If you mix your relay ground with other grounds it is likely to make issues.
 

nikhilmahasvar said:
Have you taken a separate track for your relay transistor ground ? If you mix your relay ground with other grounds it is likely to make issues.
Click to expand...

Separate track means..?
All ground will connect in same point.

Can you explain it.I can't understand the concept.
 

For relay ground you can take a track directly to input ground. Don't mix it with the ground plane till it reaches power supply ground.
 

nikhilmahasvar said:
For relay ground you can take a track directly to input ground. Don't mix it with the ground plane till it reaches power supply ground.
Click to expand...

Input from battery directly given to 7805 regulator.As per your advice,the input to BC547(which controls relay operation) have to connect to 7805 regulator and input ground's junction..Right..?
 

I can't see why two 5V regulators are needed but the main problem is there is no input capacitor at either of them. This is probably causing instability and would explain why a 5V regulator is only producing 4.5V output.

Brian.
 
Please use one 25-100uF capacitor at the input of the regulator as suggested above;

Two regulators are not needed;

Use a ceramic cap (0.1uF) close to the output pin of the regulator;

Use a storage capacitor 10-47uF capacitor for the 5V rail;

Use a 0.1uF ceramic cap close to the power supply pins of the microcontroller;

Use a 0.1 uFcapacitor in parallel with the diode (relay coil snubber).

Moral of the story: you should not be stingy with the bypass caps and use storage capacitor as a simple measure of good habit.
 
betwixt said:
I can't see why two 5V regulators are needed but the main problem is there is no input capacitor at either of them. This is probably causing instability and would explain why a 5V regulator is only producing 4.5V output.

Brian.
Click to expand...



May be some issues in regulator or I have to check is their any error in multimeter.
I planned to use two power supply separately for main power and UPS connection.

I will replace one regulator.

- - - Updated - - -

betwixt said:
I can't see why two 5V regulators are needed but the main problem is there is no input capacitor at either of them. This is probably causing instability and would explain why a 5V regulator is only producing 4.5V output.

Brian.
Click to expand...


If capacitor is the issue means then how it working with the 12V adapter.?
 

UPS output may have some EMI components and they possibly hang-on the uC.Check the main input with an oscilloscope.
A EMC filter is highly recommended at the main input of that circuit or a Ferrite Bead on the VDD of the uC.Meanwhile, the regulators are feedback devices and they should have at least one stability capacitors at their outputs.It can be something 0.1uF-1uF etc.
 

The capacitor should be at the regulator INPUTs to maintain stability. It may work with one PSU and not another due to the differences in impedance on the 12V feed but regardless, the capacitor should be there and should be very close to the regulator pins.

Why not combine the two 12V sources with diodes and use a single regulator?

Brian.
 

Thanks for your support friends,now it working fine...The MCU not hanging down.
But their is an another one problem.
Refer SW1 in diagram.
This switch is used to,switch on the buzzer.When the circuit is used with 12V adapter switch working fine.While connecting the circuit with battery power and pressed the switch means the whole unit is shutting down like shorting the negative and positive supply....Even the LED1 also switched off..
How to make the switch which work under battery condition also..?
 

Closing SW1 should only increase the current consumption by 5mA but to pull the supply down it means far more current is flowing through it. Possibilities:

1. a wiring problem around SW1.
2. R3 is a much lower value than 1K.
3. Pin 6 of the PIC is configured as an output instead of an input.

Brian.
 
You put a 0.1uF ceramic cap across SW1 contacts. That will debounce the switch to some extent.

Increase R3 to 10K - see post #12.

Your battery capacity is too small- something is shorting the battery for a moment and the circuit is getting reset.

Use a 12V battery, connect to the same regulator input via a diode. What kind of batteries you are currently using?
 

c_mitra said:
You put a 0.1uF ceramic cap across SW1 contacts. That will debounce the switch to some extent.

Increase R3 to 10K - see post #12.

Your battery capacity is too small- something is shorting the battery for a moment and the circuit is getting reset.

Use a 12V battery, connect to the same regulator input via a diode. What kind of batteries you are currently using?
Click to expand...


Its 12V 9Ah battery.Now using only one 7805 regulator.
 

Put a storage cap close to the microprocessor. Also put a small resistor in series with the buzzer.

I hope that will cure the disease.
 

c_mitra said:
Please use one 25-100uF capacitor at the input of the regulator as suggested above;

Two regulators are not needed;

Use a ceramic cap (0.1uF) close to the output pin of the regulator;

Use a storage capacitor 10-47uF capacitor for the 5V rail;

Use a 0.1uF ceramic cap close to the power supply pins of the microcontroller;

Use a 0.1 uFcapacitor in parallel with the diode (relay coil snubber).

Moral of the story: you should not be stingy with the bypass caps and use storage capacitor as a simple measure of good habit.
Click to expand...

"Use a 0.1 uFcapacitor in parallel with the diode (relay coil snubber)" is resistor is required for snubber..?
 

venkates2218 said:
"Use a 0.1 uFcapacitor in parallel with the diode (relay coil snubber)" is resistor is required for snubber..?
Click to expand...

As the relay is rather small and low power, no resistor is needed for the capacitor or the diode.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top