# ATmega328P control thirty MC14094B

Now i have a project to control more than 200 relays ,so i wanna use MC14094B(Something like 74HC595 ) to control all of it ,is it possible to push all of it without buffer or something else?

I don't know how to calculate the needs of per pin current(DATA SCLK LATCH OE) from ATmaga328P to MC14094B .

I have check the datasheet of the Atmega328P that per pin for Max 40mA , but i don't know per pin from MC14094B need how much current for it , or the shift register just need the few current but just a voltage level?

I'm new in this area hope all seniors give me some suggest or teach me how to calculate the current from it .

Thanks all first .

TPIC6B595 shift registers if relays are <= 100mA.
12volt relays draw less current than 5volt relays.
Leo…

Many relays are available in low power versions, and with that many you might want
to explain why relays - there may be other simpler alternatives...

I think you are asking how much control current must be provided by the 328P to drive the shift register(s) inputs.

The current is very low.

Please look at TPIC6B595 specification, Table 6.5

• Parameter IIH (input high) = 1µA
• Parameter IIL (input low) = -1µA

Pretty much all the CMOS devices require very low current for inputs.

Wawa:
TPIC6B595 shift registers if relays are <= 100mA.
12volt relays draw less current than 5volt relays.
Leo…

I use 12v relay and i will not direct to control relay , i’ll add maybe a N-MOS between . Thanks!

MarkT:
Many relays are available in low power versions, and with that many you might want
to explain why relays - there may be other simpler alternatives…

I think if i use other circuit to make something like DPDT it will cost more space then a relay.Thanks!

JohnRob:
I think you are asking how much control current must be provided by the 328P to drive the shift register(s) inputs.

The current is very low.

Please look at TPIC6B595 specification, Table 6.5

• Parameter IIH (input high) = 1µA
• Parameter IIL (input low) = -1µA

Pretty much all the CMOS devices require very low current for inputs.

Yes, that what i’m asking for , so what yo said about TPIC6B595 is pretty same as MC14094B?

I have take a look at MC14094B’s datasheet.

There’s a “Input current” at electrical characteristics is that the same with IIH and IL?

Can i ask u a additional question?

That TPIC6B595’s datasheet has mention “ICC” Max with 300uA at the same Table 6.5

Is that mean if i use those 8 output contorl .The Max output current will be total 300uA ? Thanks.

That TPIC6B595's datasheet has mention "ICC" Max with 300uA at the same Table 6.5
Is that mean if i use those 8 output contorl .The Max output current will be total 300uA ? Thanks.

No,

Icc is the maximum current required into Pin 2 (Vcc) when operating the chip.

Note the "outputs" are actually switches to ground. Their current does not flow through Pin 2.

superme55557:
I use 12v relay and i will not direct to control relay , i'll add maybe a N-MOS between . Thanks!

Seems you don't understand.
The TPIC6B595 is the same as a common 74HC595 shift register, but has n-channel fet outputs.
NO external fets needed.

The TPIC6B595 can drive eight 12volt relays directly.
Assuming the relays draw less than 150mA each.
As an example, 12volt blue sugarcube relays draw about 35mA.

Relay power (12volt) is connected to the relays, not to the TPIC.
The TPIC draws almost nothing from the 5volt pin and the three control pins of the Arduino.
And only three pins are needed for a whole string of TPIC chips.

You will have build problems with 200 relays, so start small and expand as your skills grow.
Leo..

You will have build problems with 200 relays, so start small and expand as your skills grow.

You will have problems, why do so many beginners try and do impossibly large projects first off?

We don’t even know why you want that many relays nor what sort of load they are switching. The EMI from that many relays can probably take out small aircraft if you are not cairful.

Assuming each relay takes 100mA, that is 20 Amps you need for the relays alone.