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[on:]

Hi All

I have a simple light timer based on the ATmega328..

It has a push button to set time(just hour ), a small LED  and a DS1307 for RTC.

The problem now that we have is the DS1307 does over heat soon after connecting the circuit to the 5v..


I have attached the schematic. I have triple checked for all shorts,etc.. im stuck.

The DS1307 heats quickly A LOT.

[Reply #1 on:]

I removed the ATMEGA from the dip socket and still it overheats. I have swapped many DS1307s and it happens on all of them.

[Reply #2 on:]

Try placing a 100 ~200 ohms resistor between the Atmega's VCC and the DS1307.

[Reply #3 on:]

Lowest I have is about 560 Ohms will that do?

[Reply #4 on:]

Try placing a 100 ~200 ohms resistor between the Atmega's VCC and the DS1307.

Not sure what good that would do. You must be missing something, they shouldn't heat up. Sounds like you may have a lot of fried DS1307s at this point. If you have any unused ones yet, stop! Upload a picture of the circuit instead.

[Reply #5 on:]

You are missing pullup resistors on SDA, SCL, I don't that will cause overheating tho.  Unless the uC is driving the pins high as regular digital outputs and not I2C/Wire outputs.
Any chance the devices are just being installed 180 degrees around? That would certainly make them warm.

[Reply #6 on:]

Make sure Vbat is connected correctly, the + side is the "back" of the cell.  Remove all ICs, check for shorts with the DMM and then apply power and verify voltages at the socket pins.  Check all pins to be sure power or ground isn't shorted to one unexpectedly.  You should have quit after two. 

[Reply #7 on:]

I feel like something is wrong on the soldered board do you need photos ? I gave schematic on the above post.

When i connect the breadboard version to the computer using USB / 5v rail from the UNO board, it doesnt over heat.

Over heating happens ONLY when we use a wall wart (+12v) connected to my own voltage regulator which uses 7805 with 470uF and a 100uF capacitors ( with 2 104 ceramic capacitors )

could this be due to the voltage regulator?

Also note my ds1307 dont seem to be frying because when i use the breadboard version they are working.. I ve used like 3 of them haha hopefuly they are not all dead yet.

[Reply #8 on:]

Make sure Vbat is connected correctly, the + side is the "back" of the cell.  Remove all ICs, check for shorts with the DMM and then apply power and verify voltages at the socket pins.  Check all pins to be sure power or ground isn't shorted to one unexpectedly.  You should have quit after two. 

Vbat is correctly connected the cell.. , I do not have any ICs apart from the Ds1307, checked shorts, etc allready for many hours lol.

Please check my schematic and let me know if everything looks OKAY there, I can wire all up from the start again and see if that would fix.

[Reply #9 on:]

You are missing pullup resistors on SDA, SCL, I don't that will cause overheating tho.  Unless the uC is driving the pins high as regular digital outputs and not I2C/Wire outputs.
Any chance the devices are just being installed 180 degrees around? That would certainly make them warm.

I thought the ATMEGA has internal pullups on the SDA/SCL i could be wrong? . like i said I dont even have the ATmega inserted on the setup and it would still over heat..

No i think they are not 180 deg

[Reply #10 on:]

I thought the ATMEGA has internal pullups on the SDA/SCL i could be wrong? . like i said I dont even have the ATmega inserted on the setup and it would still over heat..

It does, and if the Wire library is being used, it will enable them. It will probably even work this way, but the pullups are technically too weak. External pullups between 2.2K and 4.7K would be best. But either way, this will not cause overheating.

Four posts in you tell us about the voltage regulator. Have you measured its output?

[Reply #11 on:]

I thought the ATMEGA has internal pullups on the SDA/SCL i could be wrong? . like i said I dont even have the ATmega inserted on the setup and it would still over heat..

It does, and if the Wire library is being used, it will enable them. It will probably even work this way, but the pullups are technically too weak. External pullups between 2.2K and 4.7K would be best. But either way, this will not cause overheating.

Four posts in you tell us about the voltage regulator. Have you measured its output?

Jack,

I do use the Wire library lol.. A software engineer cannot talk the I2C's,etc himself haha..
Yeah output it fine.. 5V exact.

Now I tried to just use the output from voltage regulator to the DS1307 VCC and GND and nothing else.. it doesnt heat up.
Im trying everything from scratch .


Jack, please look at the schematic, then tell me THIS WILL do the job.. I would wire all the things carefully on a larger solder board and try.