# Eprom



## lefleuron (May 22, 2010)

Guys,


I am having problems with one of these "I think". This plant has some very old Barber Coleman temperature controllers. For 6 months, when the power was off for 30 seconds or longer, this controller would lose all memory.

3 months ago, we changed out the EPROM chip. This seamed to help for a little while, then this controller would lose memory at any time. Power on/ or off didnt matter.

We thought defective chip. Purchased another- different maker and a higher end product (price wise). Same thing happens.

This is one controller, and its integrated with 11 others. When this one faults, the entire process stops.

What I am wondering is this, do one of the pins on these chips control memory retention? Say, if that pin goes high- memory is erased?

And if that is the case, would a guy be able to cut the trace to that pin and install some type of switch just for programming?

I believe these things are from mid to late 70s. And no, they will not replace them. They just want us to figure out how to keep them going for them.


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## Pokesomi (Jan 13, 2011)

generally speaking no. EPROM stands for Erasable Programmable Read Only Memory. That means that it needs constant power in order to retain its memory. Similar to the Ram in your computer. What you need is an EEPROM. Electrically Erasable Programmable Read Only Memory. These are what are currently used in PLC systems and Most Flash memory based items. From iPod to your cell phone. The benefit of these is that it takes a lot to erase the memory. 
Perfect example is a PLC. When you write a program for a PLC The software sends a signal to wipe out the existing memory. Then it writes the new program to the memory.

Find out if the controller you have can use an EEPROM or if you need to upgrade the unit.


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## MDShunk (Jan 7, 2007)

You're working on a dinosaur. Sounds like your controller is flaking out... Not the EEPROM.


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## Current (Jul 4, 2011)

Call an electrician.


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## Pokesomi (Jan 13, 2011)

as with any electronics yeah the control program might be having an issue. It may be nessecary to upgrade the unit.


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## lefleuron (May 22, 2010)

MDShunk said:


> You're working on a dinosaur. Sounds like your controller is flaking out... Not the EEPROM.


 I work with a lot of dinosaurs. Its pretty much what every place has been doing for a long time, maybe when the economy gets better they will upgrade to 1992.:laughing:


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## A Little Short (Nov 11, 2010)

lefleuron said:


> Guys,
> 
> 
> I am having problems with one of these "I think". This plant has some very old Barber Coleman temperature controllers. For 6 months, when the power was off for 30 seconds or longer, this controller would lose all memory.
> ...


Not sure of your setup, but look on the board for a battery. Probably looks like a watch battery but it could look different. It sounds like you are losing the short term memory and the battery should take care of that.


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## lefleuron (May 22, 2010)

Pokesomi said:


> generally speaking no. EPROM stands for Erasable Programmable Read Only Memory. That means that it needs constant power in order to retain its memory. Similar to the Ram in your computer. What you need is an EEPROM. Electrically Erasable Programmable Read Only Memory. These are what are currently used in PLC systems and Most Flash memory based items. From iPod to your cell phone. The benefit of these is that it takes a lot to erase the memory.
> Perfect example is a PLC. When you write a program for a PLC The software sends a signal to wipe out the existing memory. Then it writes the new program to the memory.
> 
> Find out if the controller you have can use an EEPROM or if you need to upgrade the unit.


 I will look into an EEPROM. Hopefully there is something out there that will replace this.

I know they will not want to upgrade. This place doesn't upgrade until the fat lady has sung at least three times. Thats why they dont consider a late 70s system to be that old.


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## MDShunk (Jan 7, 2007)

Little-Lectric said:


> Not sure of your setup, but look on the board for a battery. Probably looks like a watch battery but it could look different. It sounds like you are losing the short term memory and the battery should take care of that.


I THINK the Cole-Parmer PLC's were OEM'd by Texas Instruments, and I don't think they had a battery.


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## lefleuron (May 22, 2010)

Current said:


> Call an electrician.


 I guess you dont have to hold your breath waiting for the phone to ring ....:laughing:


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## MDShunk (Jan 7, 2007)

Current said:


> Call an electrician.


If you find a regular electrician who even has seen a Cole-Parmer PLC, call me! 

The were peculiar to labs, pharmaceutical, food, and other delicate applications. They were sold as an engineered package, and were relabeled PLC's of some other brand.


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## Current (Jul 4, 2011)

MDShunk said:


> If you find a regular electrician who even has seen a Cole-Parmer PLC, call me!


Inside joke.


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## A Little Short (Nov 11, 2010)

MDShunk said:


> I THINK the Cole-Parmer PLC's were OEM'd by Texas Instruments, and I don't think they had a battery.


That's why I said I didn't know his setup. This mimics the problem with a dead battery though. I don't know that piece of equipment so I can't say for sure, you're probably right, knowing at least something about them. I had a machine once that I was working on that lost it's memory every time it was powered off. I looked everywhere for a battery but didn't see anything that resembled one. I finally took my high powered magnifying glass and looked the board over good. I found the markings on the board identifying the components and found the battery symbol. If you just gave it a quick look, it looked just like a capacitor. I'm sure they're probably used a lot but most of the ones I had seen were like the watch battery.


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## robnj772 (Jan 15, 2008)

Current said:


> Inside joke.


And he was swearing up and down he wasn't lefeuron :lol:


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## Jlarson (Jun 28, 2009)

Pokesomi said:
 

> EPROM stands for Erasable Programmable Read Only Memory. That means that it needs constant power in order to retain its memory.


EPROMs are non-volatile. They don't need power to retain. The only big difference between EPROMs and EEPROMs is the programming and erasing.

Sent from my Droid


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## Pokesomi (Jan 13, 2011)

Jlarson said:


> EPROMs are non-volatile. They don't need power to retain. The only big difference between EPROMs and EEPROMs is the programming and erasing.
> 
> Sent from my Droid



Correct. I should have included that.


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## Frank Mc (Nov 7, 2010)

Hi

As mentioned look for an onboard battery......Or if there's a ram chip check the socket that its plugged into...Some have a DAllas chip to hold up the ram and real time clock '..

Frank


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## nitro71 (Sep 17, 2009)

Perhaps you can power these from a UPS of some sort? Might be worth looking into.


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## Wirenuting (Sep 12, 2010)

A small UPS will work for you. 
The same kind that you can use for your computer. 
Just change the battery every 2 years. 
I've had to do that in the past and it works great.


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## JRaef (Mar 23, 2009)

I agree that an EPROM is _*not *_power dependent, it is only erased by exposure to UV light (for something like a half hour). This does not appear to be an EPROM problem in my opinion.

But most architectures that use an EPROM use it to store base data, not operating data or settings. Those would be stored in EEPROMs or RAM with a battery backup. The problem with EEPROMs is that they have a finite number of write cycles to them, often 1,000,000 in non-MIL spec systems. So if you have a system that needs to store it's data once per day, 1,000,000 days is longer than any of us will care about (2,740 years). But if it has to constantly store data, i.e. once per minute, then it's only good for 1.9 years! So for that reason, people still use a lot of battery backed RAM instead of EEPROMs.

I think you have a dead RAM battery. At first it would only lose memory when powered down because there was not enough battery voltage to maintain the RAM state without power from the power supply. But as you continue to ignore it, the dead battery becomes a drain on the power supply that drops the bus voltage below what is needed to maintain the RAM status even while running. 

Find and change the battery. It's probably one of those watch battery styles on a clip attached directly to a PC board somewhere, hopefully with easy access.


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## A Little Short (Nov 11, 2010)

JRaef said:


> I agree that an EPROM is _*not *_power dependent, it is only erased by exposure to UV light (for something like a half hour). This does not appear to be an EPROM problem in my opinion.
> 
> But most architectures that use an EPROM use it to store base data, not operating data or settings. Those would be stored in EEPROMs or RAM with a battery backup. The problem with EEPROMs is that they have a finite number of write cycles to them, often 1,000,000 in non-MIL spec systems. So if you have a system that needs to store it's data once per day, 1,000,000 days is longer than any of us will care about (2,740 years). But if it has to constantly store data, i.e. once per minute, then it's only good for 1.9 years! So for that reason, people still use a lot of battery backed RAM instead of EEPROMs.
> 
> ...


See posts #7 & 13


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## JD_ (Jul 8, 2011)

I hate RAM batteries. 

I know we've added larger batteries to stuff before.


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## Jlarson (Jun 28, 2009)

JD_ said:


> I hate RAM batteries.
> 
> I know we've added larger batteries to stuff before.


Yeah. Lots of times I'll pop the coin holder off the board and hack a cr123 cell holder in.

Sent from my Droid


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## PsiMan84 (Oct 29, 2010)

Look for a watch type battery and even look for a capacitor that is used to store backup power for the memory on the board. It doesn't always look like a battery and that could be whats going on.


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## PsiMan84 (Oct 29, 2010)

also look into maybe Flash Erasable Programmable Read-Only Memory FEPROM


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