Dear Team,
Am using Mq-03 Alcohol sensor ,And i used lm 7805 to give supply to the sensor, But i found that the regulator ic is Over heating, Can anybody suggest a solution.

Regards,
Ajin nadh.v.a
R&D Executive
Keltron Itac.

 

First, post a schematic.

How do you know it is over-heating? The finger test is not a reliable indicator since the case of an un-heatsinked 7805 (with metal case) can feel very hot but be within the regulator's allowable thermal range. The 7805 has an internal over-temperature shutdown, and if the output voltage is low (much less than 4.75V) then either you are drawing too much current or it is too hot.

Make sure everything is connected correctly.

Check that the power dissipation (volts in - 5V) x current is not too high. -How much current should/does your sensor require, what is the input voltage to the 7805 and what kind of heatsink do you have on it (in degrees C per watt if you know)?

There may be other factors that can become apparent upon examination of the schematic.

 

That sensor has a 33 Ohm heater in it so you are taking at least 150mA.

 

The datasheet says power consumption is 750mW@ 150mA, so an heatsink is required.

 

First, post a schematic.

How do you know it is over-heating? The finger test is not a reliable indicator since the case of an un-heatsinked 7805 (with metal case) can feel very hot but be within the regulator's allowable voltage range. The 7805 has an internal over-temperature shutdown, and if the output voltage is low (much less than 4.75V) then either you are drawing too much current or it is too hot.

Make sure everything is connected correctly.

Check that the power dissipation (volts in - 5V) x current is not too high. -How much current should/does your sensor require, what is the input voltage to the 7805 and what kind of heatsink do you have on it (in degrees C per watt if you know)?

There may be other factors that can become apparent upon examination of the schematic.

Dear Sir,

The datasheet says power consumption is 750mW@ 150mA, so an heatsink is required.

Dear Sir,
I already used the heat sink, But its become too hot.. Actually there is an internal shortcircuit na...?

 

Really depends on the input voltage and the type of 7805 being used.

 

Pls find the circuit...i tried this

 

Ok, have you measured the current its using?

 

Ok, have you measured the current its using?

no sir

 

Pls find the circuit...i tried this

Lovely drawing but that doesn't tell anyone anything about the power supply or the regulator.

 

Are you using an Arduino and it's on-board regulator by any chance?

 

I still wonder whether it is over heating.

Please measure the input current into the 7805, input voltage to the 7805, and output voltage from the 7805, and tell us.
Also, please describe your heatsink (shape, rough dimensions).

 

I still wonder whether it is over heating.

Please measure the input curren00t to the 7805, input voltage to the 7805, and output voltage from the 7805, and tell us.
Also, please describe your heatsink (shape, rough dimensions).

Dear Sir,
Am also using op amp to amplify the sensor out, is it may be the problem...?
The Other details will post soon...

Regards ,
Ajin

 

Yes, it might be. Eagerly looking forward to the other details.

 

I agree with DickCappels. Measure the current. If it is within range, it is fine, but if added measures are required (or wanted), add a little thermal paste and a decent heat sink and you should be fine.

 

Dear Sirs,
The overall current for the system is 5.33ma and the voltage is 13.05v

 

That doesn't add up. 5.33 ma and 13.05 volts is only 70 milliwatts, which is within the capabilites of all of the 7805 regulators I've see and not enough to get any of them very warm to the touch.

What makes you think it is overheating? Is the output 5V and within tolerance (typically ±0.25V)?

If possible, post the circuit that includes you 7805.

 

I'm confused by that. If you are saying that the output after the LM7805 is 5.33mA and 13.05V, then i would say the input is too high and you fried the regulator. Otherwise, that is not enough to short or damage the regulator if that is the input side, let alone generate a substantial amount of heat.

 

I'm confused by that. If you are saying that the output after the LM7805 is 5.33mA and 13.05V, then i would say the input is too high and you fried the regulator. Otherwise, that is not enough to short or damage the regulator if that is the input side, let alone generate a substantial amount of heat.

Dear sir,
This is the overall current( input of 7805) and voltage..........

 

Do you have a full schematic already drawn up or are you able to draw one up for us to look at?