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MOSFET or similar devices that hold their state when unpowered.

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jrodh

jrodh

Electrical
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Hi,

I am trying to identify a solid state device that will retain it's state when not powered. For example, I know that flash memory stores it's state by means of a floating gate that is capacitively charged and isolated from the drain/source. Unfortunately, I need a single discrete solid state device that will do this while passing a fair amount of current (>1 amp). I have considered a solid state relay, but I can not find a design that can retain it's state like a mechanical latching relay when it looses power.

Does anyone possibly know of a single discrete device that has such a capability, or a small circuit that could somehow manage to do this? I simply cannot find a solution using solid state devices.

Thanks
 
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A magnetic reed switch with bias coil, controlling a solid state switch.
Commercial devices based on that principle were available 50 years ago.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!
 
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Bills got the standard there.

If the state is expected to continue while NOT being commanded then an SCR will do that. After being triggered ON it will continue to stay ON until current flow drops to the cutoff level which is quite low. If it's not triggered ON then it will 'remember' to stay OFF.

Keith Cress
kcress -
 
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Didn't core memory require frequent reading and rewriting? Don't know,just asking.
Another approach may be a very low power pilot circuit with a battery that will power it for years. The battery could also be recharged each time that power is available.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!
 
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Core was permanently magnetized until erased and rewritten. However, the reading process was potentially destructive, detecting the difference in hysteresis from an applied pulse, so a write cycle was required to restore the data.

(Off topic - my favorite data storage was the acoustic wire torsion spiral. Puslses go in, the twists traveling at the speed of torsion, to the output where they would either be amplified and re-torqued or replaced.)
 
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Are you guys talking about the Apollo capsule computer?


64 bits of core memory in the 1960's took about the same space as 64 gigabytes of flash memory today (which uses quantum tunneling BTW).

jrodh,
I don't know much about what I'm talking about but I want to try a guess:
Do JK flip-flops return to their default state when power is removed&applied, or remain in their current state?
 
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When I was teaching Boolean based solid state logic, I used to teach the three states of binary devices.
In coin the flipping analogy, that would be; Heads, Tails and In Your Pocket.
When you pull the coin out of your pocket you don't know if it is heads or tails.
The gates that we were working with, memory gates, flip flops, sealed ands, and almost anything else that changed state, were in an unknown state when they were powered up. That was the "In Your Pocket" state. When a circuit was powered up, the first action was to send a reset signal to set the indeterminate gates to a known level.
That was before integrated circuits. Our gates were built with discrete components. More modern IC gates may have an internal reset function.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!
 
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Here is a description of a reed relay circuit.
G E said:
The retentive MEMORY logic function is a modification of the off-return MEMORY, with the difference being what occurs upon restoration of system power. The retentive MEMORY will resume its previous output condition, whereas the off-return MEMORY returns to the OFF condition. As evident from Fig. 11·15, the output condition the flip-flop assumes depends upon where the unit reset is connected.

With the unit reset connected to AND-NOT B2, the retentive MEMORY will return to the OFF condition, and an ON signal will be present at terminal 7 when system power is established. With the unit reset connected to AND-NOT A2, the M EMORY will return to the ON condition, and an output will exist at termi­ nal 8 when system power is established.

A completely sealed single-pole double-throw reed switch is used to perform this switching function. Referring to Fig. 11·15, we see that permanent-type bias magnets hold the movable pole to its respective side of the switch, depending on which way the coil around the switch caused the movable reed to position itself. The coil, connected between terminals 7 and 8, creates sufficient flux to override the bias magnets. Current will flow in either direction through the coil, depending upon which out­ put terminal is at zero volts and which is at -4 volts.

The reed switch has essentially an infinite mechanical life, and in this application switches no current when the movable reed moves. Current is carried, but not switched, during a brief

Fig. 11·15 Block diagram of the retentive MEMORY. (General Electric

period that system power is applied, that is, during the period when the unit reset delays its continuous ON signal. Thus the mechanical and electrical life of the reed switch in the retentive MEMORY is very compatible with the reliability of the transis­ torized static system.

The speed of operation of the retentive MEMORY is not de­pendent upon the speed of the reed switch. The flip-flop can switch at its maximum rate, and the reed switch can follow at a slower rate, as the last position the reed switch is in when power is lost determines its retentive position. The slow decay of 12-volt d-e power upon loss of 115-volt a-c system power is quite adequate to switch the reed to its proper position.
Click to expand...
image_fs8zaq.png

This also illustrates the set/reset needed on start-up.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!
 
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A couple of years later, PLCs hit the market and Solid State Logic was obsolete overnight.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!
 
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Core memory retains it last magnetization state. All computers of the 60's into most of the 70's used core memory. As for Apollo, there was this excellent series of many parts where an Apollo computer was carefully restored to operation to mark the 50th anniversary of Apollo 11. This particular computer was used in a ground simulator. Bought by a individual in a lot of Apollo surplus equipment. By the last of the series when the computer is running they are able to read-out the core memory and determine the latitude of where the computer was last operating (Houston) and determine what programs it was last executing.
Apollo Guidance Computer Part 1: Restoring the computer that put man on the Moon
 
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Other things that "hold their state when unpowered" are fuses and latching relays.
 
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If you're going to THAT route, it would be easier to use a conventional EPLD, which would be my suggestion anyway.

Use the EPLD for state storage and its output drives the power MOSFET; that combination would be TINY compared to pretty much any alternative. The fact that the EPLD stores several orders of magnitude more states is irrelevant; the space-claim would be about the same for a single state storage.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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electronic programmable logic device - presumably.

I think it needs its own power supply to produce an output so if the charge bled from the MOSFET gate it would not replenish it otherwise.
 
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Erasable Programmable Logic Device.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!
 
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Harder to guess - more results for "electronic" at the top of the Google return list.

Also in the running - Electronically Erasable Programmable Logic Device.
 
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It used to be EEPLD, when I was a LOT younger, but I think we lost an "E" along the way.

EPLDs are not volatile, i.e., they retain state with zero power and typically, the manufacturers claim 10-yr retention.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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