Need to clarify on Batteries configuration

5v battery configuation

Hello everyone,

I would need to clarified on the batteries configurations using 8 1.5V/LR6 (AA) batteries to achieve a +5V, GND and -5V output.

Please take a look at my configurations and correct me if i did something wrong and also feel free on advising me with better alternative.

Regards,
Nicholas Tok

Your circuit wastes 5mA from the batteries.
Its outputs will be +5V and -5V only when the batteries are brand new and there is no load current from the 5V outputs.

Audioguru said:

Your circuit wastes 5mA from the batteries.
Its outputs will be +5V and -5V only when the batteries are brand new and there is no load current from the 5V outputs.

Click to expand...

As for the load, it will be supply to a Ultrasonic Sonar sensor and a AD654 Voltage to frequency converter, both load will be powered by 5 VDC

This was what I was puzzle about. as the Alkaline batteries in the market is range from:

LR6 1.5V (AA)
LR3 1.5V (AAA)
LR14 1.5V (C)
LR14 1.5V (C)
LR1 1.5V (N)
4LR61 6V (J)
LR22 9V (PP3 / E)

There is no exact value of 5V battery in the market

do you have any good suggestion on achieving an exact +5V & -5V battery source?

You can use a 3-terminal low dropout voltage
regulator KA76L05,
http://www.fairchildsemi.com/ds/KA/KA76L05.pdf
KA78RxxC
http://www.fairchildsemi.com/ds/KA/KA78R05C.pdf
TS2950CT-5.0

HT74XX negative voltage regulator series
http://www.tranzistoare.ro/datasheets/105/170639_DS.pdf

Four 1.5V alkaline batteries produce 6V only when brand new. Their voltage quickly drops to 4.8V then drops slower to zero.

Calculate how much current your circuit uses then guess at what it does wrong when its 5V supplies are low. Then select batteries with extra voltage to be used with voltage regulators. Decide how long you want the batteries to last.

www.energizer.com have datasheets for all their batteries. They have charts and graphs that show how the voltage drops with time at certain load currents.

Hello mister_rf,

After reading the all the 3 datasheet that you have recommended, I am a little confuse, hope that you would enlighten me.

KA76L05
There is another Electrical Characteristics table in the datasheet, what do it mean by Output Voltage (I) & Output Voltage (II), why is there 2 readings?

From the Electrical Characteristics table in the datasheet, Max Operational Input
Voltage(VIN) is from Min. 26V ~ Typ. 33V, as for Typical Perfomance Characteristics "Figure 1. Output Voltage vs. Input Voltage" chart it state that when Vin is 6V, Vout will be fixed at 5V.

Why is there such a different? am I right to connect a min of 6V to achieve a 5V output?

KA78R05C
From the Typical Performance Characteristics chart, am I right when a Vin of +5V =< the Vout will be keep at +5V?

What is the use for Vdis which is pin 4 and how do I connect it?

May I know the correct types and values of the capacitor use Ci and Co
I would confirm that the value for Co is > 47 µF

HT7450
As for the HT7450 am I correct with the configurations as it has stated that its a Dual Supply configurations?

Am I correct to place the battery in a inverse way so the Vin will be -V?

If I am not wrong, as long as it is a negative voltage from -1V ~ -24V the output will remain unchanged at +5V and -5V

What should be the recommended value for R1?

There is 2 Vout and a Common, the common is the GND and which Vout supply positive and which Vout supply the negative 5V?


Sorry for all the long winded questions, as I am really not very sure with the configurations and performance, really hope that you could help me understand and to clear my doubts before purchasing and carrying out the design of the components and circuit.

Thanks in advance

Regards,
Nicholas Tok

By the way, what’s the maximum load current you will be required?
As long you have there two circuits, one KA78R05C is for maximum 0.1A and second one KA78R05C for 1A

NicholasTok said:

KA76L05
There is another Electrical Characteristics table in the datasheet, what do it mean by Output Voltage (I) & Output Voltage (II), why is there 2 readings?

Click to expand...

In the datasheet, There are two situations for the output voltage related to
Line regulation, a measure of the change in output voltage due to a change in input voltage, and

Load regulation is a measure of the change in output voltage due to a change in the load current

Output Voltage (I) VO (I) VI = 14V, IO = 10mA 4.81-5.19 V
Output Voltage (II) VO (II) VI = 6 ~ 26V, IO = 100mA 4.75-5.25 V
So you will have a clear picture of the how much the output variations are.

NicholasTok said:

Why is there such a different? am I right to connect a min of 6V to achieve a 5V output?

Click to expand...

Yes you are right. Depending on the load current we need between 5.2-5.6V on input to obtain a 5V output.
In the document you have maximum input voltage and how the Output Voltage vs. Input Voltage is related.

NicholasTok said:

KA78R05C
From the Typical Performance Characteristics chart, am I right when a Vin of +5V =< the Vout will be keep at +5V?
What is the use for Vdis which is pin 4 and how do I connect it?

Click to expand...

Vdis= Voltage disable and normally is more than 2.7V . If you connect this pin to ground you’ll have blocked the output voltage.
Pin 4 will be connected on pin 1 –input.
For this circuit the dropout voltage minimum 0.5V . Vin min=5.5V to obtain Vout=5V.

NicholasTok said:

May I know the correct types and values of the capacitor use Ci and Co

Click to expand...

As they have mentioned

Ci is required if regulator is located at an appreciable distance from power supply filter.
• Co improves stability and transient response.(Co > 47ìF)

Click to expand...

You can use a Ci=100uF and also for Co=100uF

NicholasTok said:

HT7450
As for the HT7450 am I correct with the configurations as it has stated that its a Dual Supply configurations?

Click to expand...

No, HT7450 it’s a negative only circuit.
A possible schematics is attached

Hello mister_rf,

Thanks you so much for the rich knowledge and willingness to explain to me on my doubts, I am sure to learn a lot from you. Never know that there is so much to learn in this electronics line.

Best Regards,
Nicholas Tok