I'm building an EPROM eraser from a toothbrush steriliser as described in "A Cheap UV EPROM Eraser", Silicon Chip, March 2005. I don't have the article in front of me and need to know the value of the cap that must be added. (I assume that the cap must be added to alter the timer's period.) Any other comments on the article/project are welcome.
Any help would be appreciated, Steve.
On Wed, 9 Jan 2008 14:26:32 +1100, "Steve Carroll" put finger to keyboard and composed:
Add a 1000uF cap in parallel with the existing 220uF cap.
BTW, check that your LED isn't wired with reverse polarity. Mine was. :-(
- Franc Zabkar
-- Please remove one 'i' from my address when replying by email.
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Excellent - thanks Frank. (I'll check the LED) ... Steve
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The LED was wired correctly, but they forgot to poke it into the hole in the front case, so it wasn't visible. Even better, one of the wires on the UV tube wasn't soldered on, it was attached with a hot glue gun. Despite this, it actually worked, but only lit up 4 out of 5 times. All fixed now, and a good little eraser. Takes 15 minutes. (Better than 36 hours with a UV insect tube.) ... Steve
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As a final note on this one, the LED on mine was in backwards too. I didn't realise it early on since it was still lighting. Having traced the circuit, I think thet the LED/resistor combo doubles as a snubber, to prevent excessive flyback voltage on the collector of the transistor. A novel method, but it works fine. I've since pulled out all of the original timing components and replaced them with a PIC16C711, a pot and an LCD display to set the time easily between 0 and 60 minutes. It works really well, and erases most chips in 20 minutes. A shame that Jaycar no longer sell the toothbrush sterilisers.
... Steve
On Tue, 12 Feb 2008 20:10:53 +1100, "Steve" put finger to keyboard and composed:
Thanks for the correction.
I was also thinking of replacing the timing stuff with something adjustable.
Yeah, I searched the Internet for an alternative but couldn't find anything similar.
- Franc Zabkar
-- Please remove one 'i' from my address when replying by email.
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