Relay can't turn on. Works well on 6v Power supply, but not 9v battery that goes through a 6V voltage regulator

eetech00

Joined Jun 8, 2013
3,859
If it works on the 6 volt supply then the 74HC04 is not the problem. However all 6 inverters can be paralleled for more output.
I think the TS means that when the RELAY is connected directly to the 6v supply it works.
but when the RELAY is connected to the 74HC04 OUTPUT it does not.
 

Thread Starter

Jambu

Joined Sep 15, 2021
19
For starters, if the circuit is wired exactly as shown, that hex inverter is not powered. That may be a problem. Next, the internal resistance of the 9 volt battery causes a serious voltage drop when the load is applied. If you put a voltmeter on it you will see that.. Finally, all of the parts will work quite well with a supply voltage of 9 volts. so you can bypass that regulator and remove it. That will leave you with only the battery internal resistance to contend with.
Hi! I've forgotten to draw the HEX power supple line. But it is powered in my circuit.
Also, if I were to bypass the voltage regulator and supply directly, won't it be bad on my HEX? If I didn't read wrongly, they have a supply voltage of 2-6v? Will I not damage it?
 

Thread Starter

Jambu

Joined Sep 15, 2021
19
I think the TS means that when the RELAY is connected directly to the 6v supply it works.
but when the RELAY is connected to the 74HC04 OUTPUT it does not.
The relay works fine when connected to the 74HC04 output in 6v power supply. But NOT when connected to 9v battery supply that bypasses a 6 volt regulator.
 

eetech00

Joined Jun 8, 2013
3,859
The relay works fine when connected to the 74HC04 output in 6v power supply. But NOT when connected to 9v battery supply that bypasses a 6 volt regulator.
Thanks for clearing that up. The relay requires about 30ma@5v, 37ma@6v.
So...you are connecting 9v to the 74HC04? I so, the 74HC04 won't operate safely at 9v (its probably shorting the battery).
It also won't safely operate over 25ma@6v.
 
Last edited:

MisterBill2

Joined Jan 23, 2018
18,180
OK, I was thinking of the CD4049 hex inverter which is very happy running on even 12 volts.
But the buzzing relay is the same thing as with a car battery that is weak and will not tur the starter but it will click on the solenoid. The same stuttering sound except a buzz with the relay because it is much faster. And the regulator is dropping out when the voltage from the battery drops just a bit.. That regulator must have a few volts above the output at the input to even work.
 

Thread Starter

Jambu

Joined Sep 15, 2021
19
Thanks for clearing that up. The relay only requires about 30ma@5v, 37ma@6v.
So this suggests the battery is weak or....what is the "9v battery supply"?
Are you connecting the relay across the battery +/- terminals as a test?

Actually, the 74HC04 can't operate safely at 9V. MAX=6v
Yes! That's why I used a lm7806 voltage regulator in my circuit as the supply.
So I connected it with 6v power supply, it works just fine.
However when I connect it to my 9v battery that passes through a 6v regulator, it made the chattering noise.
 

Thread Starter

Jambu

Joined Sep 15, 2021
19
Hi all, just to mention.
I even supply my 9v battery across the circuit directly without going through the 6v regulator.
But it still made the same noise.
 

MisterBill2

Joined Jan 23, 2018
18,180
Yes! That's why I used a lm7806 voltage regulator in my circuit as the supply.
So I connected it with 6v power supply, it works just fine.
However when I connect it to my 9v battery that passes through a 6v regulator, it made the chattering noise.
The chattering is because the regulator drops out when the battery voltage drops a bit. try no regulator and four 1 1/2 volt batteries for the six volts,
 

eetech00

Joined Jun 8, 2013
3,859
Hi ! So I am using Axicom v23105a500 .. and I am using a new 9v battery.
I am really bad at reading datasheet, but is this where I am suppose to read from as to how much current is needed?
Thats not the right chart.
You can estimate using ohms law with the coil resistance and operate voltage.

5/167=29.9mA
5x29.9ma=149.7mW or ~150mW
 

eetech00

Joined Jun 8, 2013
3,859
Hi all, just to mention.
I even supply my 9v battery across the circuit directly without going through the 6v regulator.
But it still made the same noise.
You are making confusing statements.

When you connect the 9v battery "without going thru the 6v regulator" are you still connecting the relay to the 74HC04?
 

Audioguru again

Joined Oct 21, 2019
6,674
Yes, the relay datasheet says its 5V coil draws a current of 30mA which is too high for the 74HC04.
But the 74HC04 might produce an output of 4V with its 6V supply which will barely operate the relay.

EDIT: If you powered the 74HC04 from a new 9V battery then you probably destroyed it since its datasheet says its absolute maximum allowed supply is 7V. Please read the datasheet before doing something like that.
 

Thread Starter

Jambu

Joined Sep 15, 2021
19
The chattering is because the regulator drops out when the battery voltage drops a bit. try no regulator and four 1 1/2 volt batteries for the six volts,
OMG it works!!!
But I would want to know why??
I would thought that a 9v Battery would have more current than 1.5volt x 4 battery??
 

Audioguru again

Joined Oct 21, 2019
6,674
A 9V battery is small and its six AAAA 1.5V cells produce a low current for a short duration.
Six AAA cells are larger and produce much more current.
Six AA cells are larger and produce much more current.
Six C cells ......
Six D cells ......

The cells are in series then their current is the same as one cell.
 

MisterBill2

Joined Jan 23, 2018
18,180
OMG it works!!!
But I would want to know why??
I would thought that a 9v Battery would have more current than 1.5volt x 4 battery??
A.G.A. has it exactly right with the explanation in post #36. It is the current capacity of the cells, not the voltage. In addition, part of the current capacity explanation has to do with the effective internal resistance of a battery, and that explanation gets long and tedious.
 

Thread Starter

Jambu

Joined Sep 15, 2021
19
A 9V battery is small and its six AAAA 1.5V cells produce a low current for a short duration.
Six AAA cells are larger and produce much more current.
Six AA cells are larger and produce much more current.
Six C cells ......
Six D cells ......

The cells are in series then their current is the same as one cell.
Thank you!
 
Top