Didn’t mean to unleash a storm with my schematic. Here’s an updated version with the comments above incorporated. I will make a version with a level shifter as well (for the second camp 
).
Please let me know of any inaccuracies.
missing/deleted image from Google+
You can do it any way you want, it’s you and those around you you would put at risk if something goes wrong. It may not, but is it really worth the risk? If 3 bucks worth of circuitry and another 10 minutes wiring it too inconvenient to bother with, you can cheat. It’s like leaving out fuses or bypassing door switches. If you disagree with me technically, please research the subject.
I spent 30 odd years designing and building industrial controls for IBM, At&T, Bristol Myers/Zimmer, Alcan, Emci and Welch-Allyn. My panels and systems are all over the world controlling energy levels capable of destroying a city block. 200 ton electric furnaces with 16 electrodes and air controls to Injectable medication vial cappers, I’ve had a hand is stuff most people don’t know exists. (and really miss it) You don’t just guess at that sort of stuff. The equipment has to pass inspection my dozens of alphabet soup organizations from OSHA to the FDA. NFPA 79 and UL part 508a. It took me years working for others to learn how to do it right. You never stop learning.
There’s no room for egos in this stuff, people can really get hurt, I’ve seen it and it stays with me.
Everytime I design something, it gets scrutiny from dozens of angles. You have to plan for what happens if each device fails. Sometimes that scraps a nice simple design. Sometimes you have to add expensive parts that only operate if something goes wrong. It’s a responsibility to do it properly though.
If there’s any chance at all someone will lose their sight or be electrocuted, you have to do it right. If the circuit YOU created fires inadvertently and blinds someone, can you live with that? I couldn’t. It’s ok to dabble with radios and lights and gadgets, but a laser is deadly serious energy.
I don’t understand this overwhelming desire to ‘cheat’ and cut corners. The K40 is scary enough already without adding to the cob jobs it already carries. I recently saw a video sent to someone suggesting they arc the high-voltage to ground. Incredibly is was sent by a K40 seller. What if someone doesn’t know better? That video is now out there floating around and will for years. Yes, you could check a CRT anode supply like that years ago, but the laser is an entirely more deadly affair.
If you put it out there, you have a responsibility not to get people hurt.
I don’t have as personal agenda here, except to keep people safe. No offense is meant toward anyone.
Regarding Peter, he’s a bully who picks on helpless victims. People come here for help, and he seems to think it’s more fun to belittle them and insult them. He’s driven away dozens of people, and banned many of them 2 days after they joined our group… Bruce Golling comes to mind. He’s a decent guy who was treated like dirt. He’s no dummy either, as Peter called him. The man built a milling machine from scratch. Recently Peter told another individual he should give up because “you’re too stupid to do this stuff anyway”. That gentleman left stating his equipment was for sale.
That’s not how what I USED to call the “friendliest group on the net” should treat those who come to us asking for help.
Not too many people will likely get to read this, as Peter goes around cleaning up after himself by erasing any negative references to Laserweb or himself. I’ll copy before posting for future reference.
This the last time I will weigh in on either of these subjects.
Those of you who have known me for very long know how I go.
Judge for yourself.
Scott
@Scott_Marshall I’m disapointed that you cant have discussions on here that are purely technical in nature, especially when you know nothing about me or my expertise.
You are not the only engineer on here with experience’s that are valid and valuable.
You are also not the only one on here with 30+ years of experience.
I take particular exception to your comments about Peter. I have found him only helpful and knowledgeable.
Although it’s the last time I will attempt to discuss the merits and weaknesses of this design with you, I am more than willing to do that with others interested in knowlege transfer, understanding of perspectives and in the spirit of collaboration for improvement.
I don’t know much about electronics (and in the spirit of disclosure you all know I’m working with Scott on his website).
Personally though, I think with something that can potentially blind me I would be happy to integrate a few extra $ worth of safety into it. My eyesight (& I would hazard every one here too) is very important to me. Definitely worth more than $3 or even $50.
Back to the original topic though, I’m actually liking this style of “diagram” though, as physically I can see what gets connected where (rather than an electronic schematic which makes absolutely no sense to me). So keep up the good work with the Fisher Price style diagrams Ulf
@Yuusuf_Sallahuddin_Y just cause you add more parts to a circuit does not necessarily make it more safe? In fact the more parts the higher the chance of failure.
This discussion should not overload and in fact emphasizes the need for interlocks along with the best control design possible.
There is nothing particularly unsafe about either of these designs but the use of level shifters has also not been proven to add additional safety.
Guys, can we all just get along for the sake of the community, all members and newcomers? I agree and support any situation where its full disclosed the possible safety hazards involved in operating and modifying this machines. All of you provide invaluable information and support to all of us without taking anything back and that’s to admire. At the end the user need to decide " with all cards on the table" what’s he feels he can handle. Keep it up boys
@donkjr Yeah, as I said I don’t really know much about electronics. Just I do know that I have seen my laser fire when it should be off. Correct interlocks & the likes (extra parts to a circuit) would prevent that issue indeed.
+Peter van der Walt For your information, I would just like to note that the work you are doing on LaserWeb & CNCWeb is highly valued by myself & many other members of this community & I’m sure others too.
Although a lot of it may go un-thanked, or even unacknowledged, without LW we’d all be up the proverbial creek without a paddle.
Ok then…,. phew… let’s get back to the adventure.
I will continue to test my setup looking for failure modes that can create unsafe conditions.
I have a sense some folks are running without interlocks.
PLEASE DO NOT OPERATE WITHOUT INTERLOCKS, they are the main component of your machines safety system. If you need help wiring them up let me know.
If you want more info on laser safety systems it’s instructive to read the requirements for class 4 lasers.