Need recommendation for EPROM eraser

[JoeG]

Now that I’m burning EPROMs, I thought that it would be nice to have a EPROM eraser. I’d like to know what others recommend. I don’t trust the Amazon reviews for the same low priced unit being offered with only a few reviews.

Also, does anyone know if a LED grow light from a hydroponics kit can erase an EPROM? I have a spare LED grow light from a kit where the pump failed.

Thank you!

Joe

[Jeff_Birt]

A grow light won't work.

I first bought one of those little plastic $20 Chinese made erasers. It never did work and was a fire hazard to boot. I then bought an older used commercial eraser for ~$50 on eBay and cleaned it up a bit. Larger than I really need but it will outlast me. Toward end of video below both units are in the shot.

[agarza]

A long time ago.... I needed to erase a lot of eproms.

The available eprom erasers that I found at that time were for about 5 eproms and very expensive.

So I built a wooden box and place a standard uv germicide lamp inside.

Similar to this one.

And in about 10 minutes they were erased.

You can do the same and just put the lamp inside a desk drawer.

[Paul Berger (Canada)]

I don't believe that there are any LEDs that provide sufficient light at the required UV wavelength. What you need it something with a germicidal tube in it. The tube look just like a clear florescent tube without the phosphor on the inside. The tubes are made from quartz glass because ordinary glass does not transmit UV light very well. I use an old industrial one made by Spectroline that works great, I also have a second smaller one made by the same company, but I don't have a try for it and the tray is required to make a safety switch in the back, to prevent exposure to UV light. I have another one that is just the lamp in an enclosure it was meant to be placed over a box that would be light proof and contain the EPROM to be erased, but it is packed away for moving, if you are still looking in a months time send me an email I should be unpacked by then.

The Spectroline erasers are very well made and any that I have seen include a timer which is desirable, I see there are a few for sale on eBay, the ones I have seen use standard germacidal lamps, so replacements are easy to find.

Paul.

[KeithB]

Garth Wilson would leave them out in the sun. I don't know if that worked though.

You might be able to get a pond sterilizer from your local garden supply.

[Jeff_Birt]

(09-07-2023 07:05 PM)KeithB Wrote:  Garth Wilson would leave them out in the sun. I don't know if that worked though.

You might be able to get a pond sterilizer from your local garden supply.

It does work in bright sunlight and can take 1-10 days depending on which type of EPROM.

[JoeG]

Thank you for all of the replies. Great video, Jeff!

I did find this video on using a UV LED to erase a eprom:
https://youtu.be/m0y9IO95PRU?feature=shared

It looks interesting. I just don’t know the detailed specifics of what he ordered, and what power source he uses (milliwatts?). So I asked those questions via YouTube.

Joe

[Garth Wilson]

(09-07-2023 07:18 PM)Jeff_Birt Wrote:  

(09-07-2023 07:05 PM)KeithB Wrote:  Garth Wilson would leave them out in the sun. I don't know if that worked though.

You might be able to get a pond sterilizer from your local garden supply.

It does work in bright sunlight and can take 1-10 days depending on which type of EPROM.

Yeah, that was for my first effort, almost 40 years ago, and it did take something like a week.  My first EPROM programmer was hand-made, totally manual, where you set the address and data with DIP switches and then push a button which triggered a 50ms programming pulse.  It was terribly prone to human error, but this was for my first home-made computer and I didn't have a computer of any kind to control any kind of programmer yet.  I found out later that the DIP switches weren't made to last nearly enough cycles for the job anyway.  But then KeithB, somewhat ahead of me in this stuff and always gracious, helped me out with a programmer he built that was controlled by his HP-71.  I took the papers with my hand-assembled code to his house and we entered and edited 256 bytes at a time on the HP-71 before programming that much on the EPROM.  That first home-made computer worked on first try; but it wasn't really useful.  It was interesting times, with anticipation of what our future in this still very immature field would hold.  A year later, I had a nice assembler, programmer, and UV eraser at work.  I still have a couple of Datarase II EPROM erasers, but it has been a few years since I've used one, and the last time before that was probably ten more years.

[KeithB]

I had the Heathkit eraser. I got rid of it, though.

[JoeG]

I had posted this YouTube video earlier:

https://youtu.be/m0y9IO95PRU?feature=shared

I contacted the person in the video and asked the following: "For us electronic novices, what household battery source or plug in wall adapter can we use to produce 100 milliwatts? Also, the ebay listing offers several types of UV LEDs. What are the specifications of what we need to order. Thank you!"

His reply was: "The wavelength of the led is the important thing to get right, when buying an led. With regards to the power supply, use 12v regulator, and use an led calculator online to work out the value of a current limiting resistor to safely limit the power into the led."

While I am grateful for the prompt reply, unfortunately for me this isn't helpful because I have no idea which UV LED to select from the listing on the ebay offering, and what power source (battery, AC adapter, etc.) I can use to power the LED without damaging it. I don't have the knowledge level of electronics to properly understand his reply in a manner that is helpful to me - very novice.

Can anyone help by deciphering his reply into what I need to acquire and use as a power source?

Thank you

Joe

[brouhaha]

(09-07-2023 07:38 PM)JoeG Wrote:  It looks interesting. I just don’t know the detailed specifics of what he ordered, and what power source he uses (milliwatts?). So I asked those questions via YouTube.

Seven years ago purchased a 1W short wave UV LED (dangerous!), and it took somewhere around 15 minutes to erase a microcontroller that normally took 45 minutes in a Logical Devices Ultralite (as shown by someone else earlier in this thread). The particular microcontroller part was an outlier for erase times. Most normal EPROMs erase much faster in the Ultralite, though there is considerable variation between vendors, part numbers, and even individual chips.

Intel specified the integrated dose to erase the original 2716 EPROM (circa 1977) at 15Ws/cm^2 at 253.7nm (a mercury emission line, used by common germicidal bulbs). The exact wavelength doesn't matter, though longer wavelengths may take longer. Wavelengths between 200nm and 300nm work well. Note that you won't get perfect coupling of the light source to the die, and you will be illuminating a larger area than just the die, so a 1W UV point source over the EPROM window will not erase the 2716 EPROM in 15s.

You should erase EPROMs longer than the absolute minimum time that satisfies an erasure check, because at that point the bits aren't actually FULLY erased. The floating gate memory cell is analog, and is amplified and compared to a threshold. At the minimum time that the part reads as erased, some of the floating gates have almost enough charge to read as programmed. You have to have some margin against temperature and voltage variations, and other unpredictable causes of variation.

Some people have used unfiltered quartz envelope xenon flash tubes to erase EPROMs with a single flash. It works, but repeated use damages the chip in fewer erase cycles than more conventional erasers.

WARNING:

Short wave UV can burn your eyes and skin, and cause DNA damage, which is how it kills bacteria. Never operate a shortwave UV (under 300nm) light source except in a light-sealed container. All UV erasers should have a safety interlock switch that cuts power when the enclosure is opened.

[brouhaha]

(09-07-2023 07:38 PM)JoeG Wrote:  I did find this video on using a UV LED to erase a eprom:
https://youtu.be/m0y9IO95PRU?feature=shared

It looks interesting. I just don’t know the detailed specifics of what he ordered, and what power source he uses (milliwatts?). So I asked those questions via YouTube.

I can't speak for the specific LED he used, but let's take as an example the Luminus Devices XST-3535-UV-A60-CE270-00, which costs $35.41 in quantity one from Digikey Electronics. This is a surface mount component, 3.65mm on a side, so probably isn't well-suited for simple tabletop experimentation, bur can serve as an example for calculations.

The peak wavelength is 270nm, and the radiation pattern is a 60 degree wide cone. The maximum current is 800mA, and the forward voltage drop is 5.0V min, 6.45V typical, and 7.5V max. Note that a heat sink (large copper area on PCB, or an aluminum core PCB) will be required to operate at maximum current to keep the LED junction (inside the package) below the maximum rating of 100 degrees C. Also, radiant flux (intensity) decreases almost linearly from 25C to half at 100C, so keeping the LED temperature down yields best performance.

For a fixed voltage power supply of 12V at 1A max, we need to compute the necessary series resistance to ensure that the current does not exceed 800mA. For a regulated 12V power supply, which should have a current rating of at least 800mA, say 1A to provide margin, and assuming the typical voltage drop of 6.45V, the resistor will have to drop 5.55V. By Ohm's Law, the resistance necessary for that, R = E/I = 5.55/0.8 = 5.625 ohms. The resistor will have to dissipate P = R*I^2 = 5.625 * 0.64 = 4.44W, so that requires a power resistor. One could use a power rheostat to get close to that resistance, but in practice one uses the next higher standard value power resistor, which would be a 7.5 ohm +/-5% 5W resistor, such as the Ohmite 805F7R5E. The resistor will need to be mounted to a heat sink.

Now we need to do the calculations using worst-case values. Assume that the power supply regulation is 5%, so it could be as low as 11.4V or as high as 12.6V, the LED drop could be as low as 5.0V, and the 5% resistor could be as low as 7.125 ohms or as high as 7.875 ohms. If we run the calculations for those eight cases, we find that all cases with the LED drop at 5V result in over 800mA of current and 5W power. Further, even at the nominal 6.45V drop of the LED, if the power supply is 12.6V and the resistance is 7.125 ohms, there will be overcurrent and overpower.

What this means is that to satisfy the current limits, we have to go to a 10 ohm 7.5W or 10W resistor. The higher resistance means that we might get current as low as 371mA, running the LED at less than half brightness.

The best way to deal with this is to use a voltage regulator configured for current regulation rather than voltage regulation. This can be done easily with three-terminal linear regulators like the LM317. The load regulation will be within +/-1.5%, so we actually set the current limit to 788mA or less. The regulator will dissipate the same power the series resistor did in the simpler method above, so worst case it will dissipate up to 7.6V * 800mA = 6.08W. The TO220 packaged LM317 can do that if it has really good heatsinking and maybe forced air cooling.

The same could be done with a switching regulator, and will dissipate much less power, but the circuit design is much more complex. There are also dedicated LED driver chips that may be useful; some use an external pass transistor which would be necessary for the described case.

For running an LED at significantly lower power, e.g. 100mA, the power dissipation issues would be less extreme, but would still need to be analyzed.

Note that the LEDs are binned into multiple smaller forward-drop voltage ranges. When you buy in small quantity from a distributor, you don't get to pick the bin, but if you buy in large volume you may be able to.

A spreadsheet I've used for this example is attached. I did this in LibreOffice, but had to save to Microsoft .xlsx format in order to be able to attach it. The spreadsheet should work in Microsoft Excel, but I'm not sure whether the conditional formatting that makes overcurrent and overpower cells show as red background will work.

[JoeG]

Wow! Thank you for those replies. It sounds like it's well over my head at this point in time. But since I'm self teaching electronics from books and online training videos, I'm sure this information will make sense when I reach that part.

Thank you for the spreadsheet! I'll keep it as a learning tool as I learn more about electronics.

As for now, I surrendered and bought a EPROM eraser off of Amazon, and the required 220 to 110 power adapter. It's not like the one Jeff bought, but it has some good and some bad reviews. I'll find out soon enough how it works when it arrives. For the price, it's worth the risk. I have 30 days to return it if it doesn't work.

This is the unit I ordered: https://www.amazon.com/dp/B08P1D558C?psc...ct_details

Joe

[JoeG]

My EPROM Eraser, along with the 220v to 110v convertor plugs, arrived today. I was able to erase the two EPROM's I burned a few days ago in 12 minutes. The cost of the EPROM Eraser when I bought it was $9.99. It has since gone up an additional $20!!! It must have been priced incorrectly, I guess.

Either way, I'm happy. If it doesn't last long, the cost was cheap.

Joe

[Bushcat]

Just for fun, I tried the kid's curing station which came as part of a resin casting kit. I've also seen it sold as a UV nail hardener. It erased one of my ancient eproms in about 10 minutes.

[ijabbott]

(09-11-2023 12:34 AM)JoeG Wrote:  As for now, I surrendered and bought a EPROM eraser off of Amazon, and the required 220 to 110 power adapter. It's not like the one Jeff bought, but it has some good and some bad reviews. I'll find out soon enough how it works when it arrives. For the price, it's worth the risk. I have 30 days to return it if it doesn't work.

If it uses a synchronous motor to drive the timer, you may find the timer runs 20% fast if it assumes a 50 Hz supply and you are running it at 60 Hz. Increase the selected time by 20% to compensate.

If it uses a clockwork motor, it's probably accurate enough!

[JoeG]

The timer on the device seems faulty enough to where I don't use it. I use a timer or a clock. So far, 12 minutes seems to be working just fine.

Joe