1 Bit permanent memory  - Page 1
Forum section: electronics / beginners

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: November 19, 2015, 10:07:55 pm
content: 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

author: ataradov
author_rank: Super Contributor
timestamp: November 19, 2015, 10:21:45 pm
content: 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.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: November 19, 2015, 10:22:42 pm
content: Quote from: ataradov on November 19, 2015, 10:21:45 pmThank you very much now i can get down designing the final circuit

author: dmills
author_rank: Super Contributor
timestamp: November 19, 2015, 10:23:24 pm
content: 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.

author: jeroen79
author_rank: Frequent Contributor
timestamp: November 19, 2015, 10:30:03 pm
content: 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.

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: November 19, 2015, 11:06:18 pm
content: i would like to be able to write and read several times... so the d type flip flop is a good solution

author: zapta
author_rank: Super Contributor
timestamp: November 20, 2015, 05:16:30 am
content: 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

author: Richard Crowley
author_rank: Super Contributor
timestamp: November 20, 2015, 06:25:18 am
content: TI "Little Logic" SOT-23 size D flip-flop

author: amyk
author_rank: Super Contributor
timestamp: November 20, 2015, 08:29:58 am
content: Quote from: Richard Crowley on November 20, 2015, 06:25:18 amThat'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.

author: rgawron
author_rank: Contributor
timestamp: November 20, 2015, 10:56:39 am
content: You may use a thyristor made from two transistors.

author: jeroen79
author_rank: Frequent Contributor
timestamp: November 20, 2015, 11:08:22 am
content: Quote from: rgawron on November 20, 2015, 10:56:39 amOr use a thyristor made from one thyristor ; )

author: Zero999
author_rank: Super Contributor
timestamp: November 20, 2015, 01:06:01 pm
content: A bistable can be made from a couple of transistors.https://en.wikipedia.org/wiki/Multivibrator#Bistable

author: Kalvin
author_rank: Super Contributor
timestamp: November 20, 2015, 01:28:21 pm
content: OP may also want to add a Led, and use it as a very cheap logic analyzer.

author: zapta
author_rank: Super Contributor
timestamp: November 20, 2015, 01:34:05 pm
content: Quote from: jeroen79 on November 20, 2015, 11:08:22 amBut how do you make the first thyristor?

author: MatthewEveritt
author_rank: Unknown
timestamp: November 20, 2015, 02:01:39 pm
content: Quote from: zapta on November 20, 2015, 01:34:05 pmOut of a thyristor, obviously.

author: Karel
author_rank: Super Contributor
timestamp: November 20, 2015, 02:17:34 pm
content: Quote from: zapta on November 20, 2015, 05:16:30 am+1https://en.wikipedia.org/wiki/Relay#Latching_relay

author: zapta
author_rank: Super Contributor
timestamp: November 20, 2015, 02:25:52 pm
content: Quote from: MatthewEveritt on November 20, 2015, 02:01:39 pmTouche.