Another UV Light Box (16x20)

[Jim Fitzgerald]

This is a great read. I've been using my NuArc 26-1ks for a long time now and would like to have a backup unit incase I have to travel to do a carbon workshop or demo. Nice job guys thanks for the info.

[sheel]

I would recommend an isolation transformer between the wall and your appliance, 120VAC input and 120VAC output while you're testing the design. I would also install an IEC receptacle with a fuse but-in or install a fuse just after the power receptacle. The switch is rated at 16amp, each ballast draws 1.15amp, and there are 3 ballasts, the fans draw insignificant amount, so you're not anywhere near exceeding 16amp rating of the switch. Why not use a DPDT switch so the fans come on automatically? A cheap ballast could have poor overload protection and would blows itself up if the load is not connected, imbalance load, or high side shorted to ground. Perhaps use a ballast with a better warranty. Do not open the ballast, it's probably beyond your level.

On the schematic, why are the switches connected to neutral?

Thanks for the feedback Jeff.

1. Isolation transformer - makes sense for protection - would a surge protector suffice, or are you referring to full on power conditioner?
2. IEC receptacle - this is a great idea; i was trying to figure out how to add fuses - something like this receptacle should be appropriate?
3. DPDT could make sense, I just kind of went with two separate switches on a whim while I was at Home Depot, as to control the lights or fans separately. They're these nice little rocker switches.
4. These Fulham ballasts are supposed to be pretty high quality (?) and even have an internal fuse... unfortunately they're sealed and not self-serviceable... Agree, I will stay away from cracking them open. No point. I definitely blew the first one with a poor connection and the second because a staple I used penetrated the return wire :|
5. Switches connected from Neutral to Ground - this could be a mistake, the last time I had all the switch connected from neutral to white/out one of the three ballasts went out. There is an LED light on the switch itself which needs power, and this does not come on if I don't have Neutral connected to Ground or Out.

Let me know if you have any other advice... I'm an electrical n00b

[denverjims]

3. DPDT could make sense, I just kind of went with two separate switches on a whim while I was at Home Depot, as to control the lights or fans separately. They're these nice little rocker switches.

I did find having separate switches was helpful. Could leave fan (I only used one) on after turning off lamps to dissipate heat faster after long exposures.
Best, Jim

[sheel]

I did find having separate switches was helpful. Could leave fan (I only used one) on after turning off lamps to dissipate heat faster after long exposures.
Best, Jim

Thanks Jim, would you be able to comment on your general circuit design vs. my approach? I'm not sure if I'm on the right path or doing something completely off - here's the current schematic.

[Jeff T]

The isolation transformer is to protect you from excessive current if you touch the black wire. Without the isolation transformer, your body completes the circuit to ground when you touch the black wire.

If it's a LED lighted switch then the Neutral lead is for the LED circuit. Update your schematic to show the LED so there's no confusion. Having a separate switch for the fans poses a great chance for overheating. Perhaps using a DPDT with a heat sensor to activate the fans would be more elegant.

Thanks for the feedback Jeff.

1. Isolation transformer - makes sense for protection - would a surge protector suffice, or are you referring to full on power conditioner?
2. IEC receptacle - this is a great idea; i was trying to figure out how to add fuses - something like this receptacle should be appropriate?
3. DPDT could make sense, I just kind of went with two separate switches on a whim while I was at Home Depot, as to control the lights or fans separately. They're these nice little rocker switches.
4. These Fulham ballasts are supposed to be pretty high quality (?) and even have an internal fuse... unfortunately they're sealed and not self-serviceable... Agree, I will stay away from cracking them open. No point. I definitely blew the first one with a poor connection and the second because a staple I used penetrated the return wire :|
5. Switches connected from Neutral to Ground - this could be a mistake, the last time I had all the switch connected from neutral to white/out one of the three ballasts went out. There is an LED light on the switch itself which needs power, and this does not come on if I don't have Neutral connected to Ground or Out.

Let me know if you have any other advice... I'm an electrical n00b

[denverjims]

Having a separate switch for the fans poses a great chance for overheating. Perhaps using a DPDT with a heat sensor to activate the fans would be more elegant.

Jeff, I didn't understand this unless you meant that it would be possible to turn on the lamps but not the fan with 2 switches. Technically, I agree but felt that low risk. I turn fan on first and don't turn it off until I'm done with my entire printing session and things have cooled down.

Heat sensor would be more elegant but also more stuff to buy and wire. I was using KISS and figuring if I did not turn on the fan, I'd deserve the consequences. Being a Libertarian, it fit right in with my personal beliefs.
Best, Jim

[jp]

If the fan is running, it is unlikely to ever heat up, so it the fan goes on and off with the light that's simple and practical too.

[denverjims]

Thanks Jim, would you be able to comment on your general circuit design vs. my approach? I'm not sure if I'm on the right path or doing something completely off - here's the current schematic.

Looks good to me (although my lawyer would suggest a more cautious response to avoid liability if you blow yourself up, I'll ignore that).

As you noted, miswiring the ballast to the lamps is the biggest risk but the ballasts usually have a wiring diagram for how they are to be used with the lamps. If it is not printed on the top of the ballast, then look the ballast designation up on the web and usually you can find wiring specs. The only other thing, as I noted in my original post, is to choose the correct 'tombstone' for the type of lamp and ballast combination you are using.

Best, Jim

[denverjims]

If the fan is running, it is unlikely to ever heat up, so it the fan goes on and off with the light that's simple and practical too.

Correct, jp, but since many alt printing process chemistries are sensitive to heat as well as UV, I decided to have a way to keep the fan on after lights went out since the lamps continue to put out heat after turning off. That way I don't have built up heat from the last, long exposure inside to start off with the next one.

Frankly, I was not sure that this would be real problem (and still am not). Many other designs I've seen do not have 2 switches so others don't think so. Maybe they are right but that was my choice and it seemed a cheap enough up front add-on to be insurance against that kind of problem. Retrofitting a second switch after the fact (if I had found it was an issue) would have been a pain.
Best, Jim

[Tin Can]

Perhaps some use an external timer to turn it off.