Idea for an cheap Eprom eraser, UV diode

[DanC]

Hi!

I was thinking of build me an cheap Eprom eraser.

Do you think this UV diode will work?:
https://www.electrokit.com/en/produc...md-6-5v-275nm/

And if so, how do you supply power to this diode?

[pandy71]

It should work, but there is no information about maximum allowed forward current - without knowing this you can't think about supplying power.
Normally i would use constant current source to deliver power - probably LM317 will be cheapest one. if you use 2 such diodes connected in series then it is chance to use standard LED power supply but still - without forward current information there is no way to calculate limiting resistor...

[DanC]

Thanks,great!

The PDF file in the link says max forward current=50mA.
Can you then calculate the limiting resistor?

And how would a schematic look with an LM317?

[derSammler]

You are better off just putting the EPROMs in the sun instead. That diode will not work, it is way too weak.

These are made to build sensors or for short-range data transfer. As such, they are very weak to make sure you can look at them without damaging your eyes. An EPROM eraser on the other hand comes in a huge metal case to make sure no UV light can escape. Guess why.

You can get a cheap EPROM eraser for less than 30 bucks already (like this: https://www.ebay.de/itm/134711089396). So why even bother?

[pandy71]

Originally Posted by DanC

Thanks,great!

The PDF file in the link says max forward current=50mA.
Can you then calculate the limiting resistor?

And how would a schematic look with an LM317?

Sorry, i've overlooked datasheet obviously.

Use this as reference https://bristolwatch.com/sr/cc_led.htm

For 50 mA current calculation is 1.25/0.05= 25..27Ohm.

[DanC]

Originally Posted by pandy71

Sorry, i've overlooked datasheet obviously.

Use this as reference https://bristolwatch.com/sr/cc_led.htm

For 50 mA current calculation is 1.25/0.05= 25..27Ohm.

Nice! Thnks again!

[pandy71]

Single LED is quite low power - only 5mW of UV - you can use more LED's, they are quite small so it can be difficult to properly dissipate heat - i would recommend special PCB (MCPCB - with aluminum or copper core but very thin regular PCB with thermo transfer adhesive can do work also) - perhaps you can use common thermo transfer adhesive tape and some flexible wire to attach LED's directly to radiator without carrying PCB.

[DanC]

Originally Posted by pandy71

Single LED is quite low power - only 5mW of UV - you can use more LED's, they are quite small so it can be difficult to properly dissipate heat - i would recommend special PCB (MCPCB - with aluminum or copper core but very thin regular PCB with thermo transfer adhesive can do work also) - perhaps you can use common thermo transfer adhesive tape and some flexible wire to attach LED's directly to radiator without carrying PCB.

Thnks! Maybe 3 or so in serie? But, do you calculate the limiting resistor the same as with only 1 LED ?

[pandy71]

Originally Posted by DanC

Thnks! Maybe 3 or so in serie? But, do you calculate the limiting resistor the same as with only 1 LED ?

there is no change when LED's are connected in series - but you need to provide sufficient voltage at LM317 input - for 3 UV LED's in series you need 3*6.5V=19.5V plus some voltage is necessary for LM317 to operate - let say you need 2..3V at least higher at input than voltage at LM317 output. so you need at least 21.5..22.5V power supply... maximum voltage allowed at the LM317 input is 37V.

[DanC]

Originally Posted by pandy71

there is no change when LED's are connected in series - but you need to provide sufficient voltage at LM317 input - for 3 UV LED's in series you need 3*6.5V=19.5V plus some voltage is necessary for LM317 to operate - let say you need 2..3V at least higher at input than voltage at LM317 output. so you need at least 21.5..22.5V power supply... maximum voltage allowed at the LM317 input is 37V.

Great! So you just need to have higher input voltage, the current is the same!

[pandy71]

Originally Posted by DanC

Great! So you just need to have higher input voltage, the current is the same!

Yes, each LED add own forward voltage so you need higher supply voltage but current stays same so resistor doesn't change.

[Photon]

Cheapest EPROM eraser is the window sill. It's slow though. But you can do it for free.

I'm guessing this isn't for kickstarts, since AFAIK the hard part is getting the right parts in EPROM form. I wouldn't mind a tiny flash board...

I think you can find both EEPROM and EPROM programmers cheap from Asia. The EPROM ones have a UV tube, not LED.

[nocash]

Using LEDs is an interesting idea, I had never though about that, and I didn't even know that those kind of bacteria-killing death ray LEDs exist.
There seem to be several people and webpages that have tried to or speculated about using LEDs for EPROM erasing. The relevant webpage from somebody who has actually done it successfully is here:
https://www.george-smart.co.uk/2021/...proms-in-2021/
The LEDs used there are a slightly more powerful, but they seem to have worked very well, apparently erasing the EPROM in less than 1 minute.

I've been wondering why everybody is suggesting to use a LM317 with one resistor (as current regulator). Alternately one could use a LM317 with two resistors (as voltage regulator), or use a power supply with known output voltage (and add a resistor in series, if needed).
I am no expert on analog electronics, but I think that all of those methods should work, each with its own advantages & disadvantages.

Current regulator that's probably best if you want to use several LEDs in series. The downside is that you need a lot of volts, like at least 19.5V in the above example, and I simply don't have such power supplies at home.
One could get away with fewer volts when using a single LED. Or when wiring the LEDs in parallel (but I think that would risk that one LED would absorb the whole current and overheat, so don't do that).

Voltage regulator with 7.5V output should be best when using several LEDs in parallel, and it should work with a standard 12V power supply (which I do have at home en masse, so that would be my preferred solultion).

No regulator, that kind of LEDs should work at 5V .. 7.5V (or the like, check the datasheet). 5V would be perfect for hooking the LED to any kind of PC, Amiga, USB power supplies. But I suspect 5V is the lower limit, where the LED would barely start to glow at minimum brightness (possibly with a 50% chance that it won't glow at all).
The next some standard voltages would be 7.5V (optimal, but not so standard, unless you have a PSone Playstation) and 12V (with resistors in series with each LED).

[DanC]

Nice link!
So he used 2 120mA diodes, and claimed he erased the eprom in 1 min!
I have not such a hurry, so if i try with one 50mA diode, 15-20 min will work for me.

I think i will try to get this up for testing, starting with just one 50mA.

Dumd question, but where do you connect + and - on this diode?
What terminal are anode and cathode?
https://www.electrokit.com/en/produc...md-6-5v-275nm/

[pandy71]

Originally Posted by nocash

I've been wondering why everybody is suggesting to use a LM317 with one resistor (as current regulator).

Constant Current Source is proper way to feed LED - excessive current will kill LED so you need be sure that you never go over specified by LED datasheet current. Voltage in case of LED is required only to LED begin conducting but every LED may and usually have this voltage different so constant voltage source with resistor may not prevent LED from being damage unless your resistor is sufficiently high to prevent this excessive current flow.
LM317 is simply very popular and very cheap, easily available universal regulator, of course you can use other approach - for example for high current probably switched current regulator will be more energy efficient but for small current this will be overkill.

[pandy71]

Originally Posted by DanC

Dumd question, but where do you connect + and - on this diode?
What terminal are anode and cathode?
https://www.electrokit.com/en/produc...md-6-5v-275nm/

In datasheet, on page, top right corner you have information about cathode location.

[DanC]

Originally Posted by pandy71

In datasheet, on page, top right corner you have information about cathode location.

Thnks! But i dont understand...

This is the pic of the diode, cathode is marked, but not so clear where?
And which strip is the anode?

[pandy71]

Originally Posted by DanC

Thnks! But i dont understand...

This is the pic of the diode, cathode is marked, but not so clear where?
And which strip is the anode?

Attachment 80669

Cathode has small notch on pad area - placed circle around notch to emphasize this detail - anode is on opposite side so based on bellow picture most left edge red area is anode, in middle you have red area probably to improve thermal conductivity and on most right side is cathode with small notch. Anode-Thermal pad-Cathode

[DanC]

Originally Posted by pandy71

Cathode has small notch on pad area - placed circle around notch to emphasize this detail - anode is on opposite side so based on bellow picture most left edge red area is anode, in middle you have red area probably to improve thermal conductivity and on most right side is cathode with small notch. Anode-Thermal pad-Cathode

Great! Thanks for explaining!! So right red strip is the Cathode, and left red strip is the Anode!

[pandy71]

This is how i interpret datasheet - you can always use multimeter on current range connected in series with your constant current source to determine anode and cathode - usually multimeters have special diode test to check semiconductor junction but in most cases voltage in such mode is not higher than 2V - this is way too low for UV-C LED where forward voltage is approx 6V.

You can find many useful information's on https://ams-osram.com/products/leds/...5-su-culbn2-vc - this should be quite comparable device.