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Problem interfacing different modules to microcontrolller

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Newbie level 5
Aug 10, 2009
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Dear all,
The attached zip file contains 2 *.bmp files.
1. present.bmp
2. Proposed.bmp

There is no software or firmware issue. It is a hardware.. kindly help me to get through. I have already spent many grands money in testing.

Problem :
1. I made the circuit as present.bmp All the components were working fine. The IP camera was a bit slow(weak) and camera motors used to malfunction (stop) after 1-2 mins of operation but the camera used to keep sending the video . So I thought that they are getting less current.
2. So I put one more 7805 in parallel as shown in proposed.bmp The complete setup worked for 10 mins then i switched it off. In the morning when I again tested the project, the ip camera motors moved for some time and then stopped. and they never moved again. done all the testing and reached the conclusion that IP camera is not switching ON. May be its power supply circuit (inside the camera is burnt (99.9% probability)).

1. Since I had connected 4 x 7805 in parallel i.e. I got a supply of 5v 4A , taking tolerance into consideration, lets say I got 5v 3.25A Now 0.5 - 0.75A is taken by micrcontroller. so we are left with 5v, 2 - 2.5A. So did the camera blow up due to large current?. Kindly correct the calculations.
2. Since at 5V camera would take only 2A, so is it possible that (in any way) 3A or more had passed through camera (blowing up the camera).
3. I am going to make the changes as shown in proposed.bmp except putting 4 x 7805 in parallel (will use 3 x 7805) .
4. kindly explain snubber circuit in simple words. have visited many sites ...but is quite complicated to understand.
5. Another portion for consideration,as you wold have noticed by now, I am using 5-6 voltage regulator there is lot of head being generated even after placing the heat sinks.. Kindly suggest something for a cooler circuit.

Kindly guide me...
Thanx a lot for your kind concern...

Re: Problem interfacing different modules to microcontrollle

This is a very unusual way of connecting 7805s in parallel for more current !
I have never seen this configuration and not sure if it should work properly!
Check datasheet of 7805. There is a way to get high current from it using a pass transistor.
In case if you don't find it, here is the schematic from the datasheet
Make sure your 7805 is mounted on a large heat-sink.

For high current I would recommend switching regulators instead of linear!

Re: Problem interfacing different modules to microcontrollle


If you search around you will see that paralleling regulator outputs is a No, No.

Put simply, each regulator has a very slightly different output voltage and although appearing to work will fail in use.

Besides why try and do this when there are so many 2A, 3A, and 5A fixed and variable regulators on the market for the same or less money ?
Plus as CMOS rightly says, you can always use a series pass transistor or SM psu.

This thing apart, plz clear a concept of mine you would have seen int the circuit, is there a possibility that 3-4Amp of current had flown through camera rated as 2A at 5V , resulting in a blow up..
Another issue was regarding the RC snubber design..plz write few lines on that....

Added after 2 minutes:

plz specify some IC for 5V and 12V, rated as 2A,3A,4A which are easily available in indian market....dont want to import IC for this purpose...

Re: Problem interfacing different modules to microcontrollle

Its not the current. I suspect higher voltage (or high voltage spikes) was applied to the camera because of unusual configuration/failure of 7805s.
A device will draw only as much current that is required for it operation. A 5V, 2A device will not draw 100A if your power supply is of 5V 100A capacity.

Here are high current switching regulators available from National
**broken link removed**
LM2678-5 and LM2678-12 seems to be good replacements for your application.

This is a very good document on snubber design

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