1 Bit permanent memory

[ChrisGreece52]

Hello i wrote again about a project i am working on and need help again ... i need a memory cell to store a 5v signal for a long time i am talking about months here... i dont need it to store the bit without power but as long as it is plugged in i need to be able to store one bit of info.
I did a google search and i found memory modules using not and nand gates but i am not sure if this is permanent or just temporary (for a few minutes)
I need your help with this .
Thank you in advance

[ataradov]

74HC574 will let you store 8 bits for as long as you like.

You can create an equivalent circuit from  NAND gates, but you won't save any space on the board.

[ChrisGreece52]

74HC574 will let you store 8 bits for as long as you like.

You can create an equivalent circuit from  NAND gates, but you won't save any space on the board.

Thank you very much now i can get down designing the final circuit

[dmills]

A "D" Flipflop, does exactly what you want, or maybe a set/reset latch, which is better depends on your available control signals.

Regards, Dan.

[jeroen79]

How about using a very low current fast fuse?
(or something else that will blow quickly at the slightest but of current)

Connect it between GND and a pullup resistor.
When read it will read Low.
To write once you connect it to VCC. Current will flow and the fuse blows.
When you read it again there is no short to GND and the pullup resistor will give a High reading.

Takes just 2 components and will retain it's value even after poweroff.

[ChrisGreece52]

i would like to be able to write and read several times... so the d type flip flop is a good solution 

[zapta]

You can use a dual coil latching relay. It will remember the bit even without power.

http://www.ebay.com/itm/10x-Panasonic-TQ2-L2-5V-Two-Coil-Latching-Signal-Relay-DPDT-5V-/321905891998?hash=item4af3161a9e:g:S1EAAOSwwbdWMdaT

[Richard Crowley]

TI "Little Logic" SOT-23 size D flip-flop

[amyk]

TI "Little Logic" SOT-23 size D flip-flop

That's so cute. I wonder if anyone has built a computer out of these... TTL and through-hole transistors have been done a few times already.

[rgawron]

You may use a thyristor made from two transistors.

[jeroen79]

You may use a thyristor made from two transistors.

Or use a thyristor made from one thyristor ; )

[Zero999]

A bistable can be made from a couple of transistors.
https://en.wikipedia.org/wiki/Multivibrator#Bistable

[Kalvin]

OP may also want to add a Led, and use it as a very cheap logic analyzer.

[zapta]

You may use a thyristor made from two transistors.

Or use a thyristor made from one thyristor ; )

But how do you make the first thyristor?

[MatthewEveritt]

But how do you make the first thyristor?

Out of a thyristor, obviously.

[Karel]

You can use a dual coil latching relay. It will remember the bit even without power.

http://www.ebay.com/itm/10x-Panasonic-TQ2-L2-5V-Two-Coil-Latching-Signal-Relay-DPDT-5V-/321905891998?hash=item4af3161a9e:g:S1EAAOSwwbdWMdaT

+1

https://en.wikipedia.org/wiki/Relay#Latching_relay

[zapta]

But how do you make the first thyristor?

Out of a thyristor, obviously.

Touche.