# What component type to use?

#### KILLERBUG

Mar 7, 2022
6
If I have a ground side controlled fan output (fixed positive voltage and the ground turns on and off), is there an easy way to turn that into a power side controlled output (fixed ground and the positive turns on an off)? Need PWM. Also the control board is 3.3v and the device is 5v if that matters...I also have 5V, 12V, and 24V available if useful. I feel like this must be common enough that it's just a chip you buy or something?

Thanks!

#### Martaine2005

May 12, 2015
4,538
Is the fan a simple on-off? Or is it speed controlled too?.
Is the PWM controller a board you want to add?. If so, what motor does the fan have and what voltage? 5V?.

Martin

#### KILLERBUG

Mar 7, 2022
6
I want to use a fan port on a Octopus board to control my laser's high voltage power supply. Power supply needs a 5V PWM signal but board only offers ground side PWM outputs. I figure there must be an adapter chip or something. If not, I might just use an arduino.

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,084
A fitting circuit is shown e.g. here. Note that you will need a so called logic level P-MOSFET (VGSth> -3 V).

Mar 7, 2022
6

#### KILLERBUG

Mar 7, 2022
6
Thank you for your confidence. I have been using the Internet to access DigiKey for over thirty years and still haven't discovered everything they offer. Alas, some problems don't seem to have a practical solution. So, maybe it's time to break out that Arduiino Uno kit you bought on a whim and set aside for future use. I did that once, playing around with Bluetooth peer-to-peer networks for awhile, but good luck with your \$400 laser power supply. BTW, what kind of laser are you using? CO2? HeNe? Some sort of solid-state laser? Forum minds are aching to know!
It's a 60w CO2 laser, started as a standard Chinese red-n-black but now it's anything but standard.

#### hevans1944

##### Hop - AC8NS
Jun 21, 2012
4,792
Wow! Sixty watts, assuming a focusable Gausian-profile beam, and a suitable lens, this is a real TOOL of a laser! IIRC, one of the moderators here recently purchased one of those Chinese wonders for integration into some sort of 3D, CNC-based, cutting machine. There are pictures somewhere on this forum.

#### KILLERBUG

Mar 7, 2022
6
Wow! Sixty watts
It used to be 90W; thus the expensive supply. Unfortunately that tube had a defect and getting a replacement at the same wattage wasn't possible at the time.

#### hevans1944

##### Hop - AC8NS
Jun 21, 2012
4,792
Working with CO2 lasers can be an expensive proposition, especially if you need to fill the resonant cavity with so-called "laser gas" periodically. I had to do this to fire up a folded CO2 bench-top laser rated for 300 watts at the Air Force Weapons Laboratory in Albuquerque NM.

Laser gas is commercially available, but this lab had a large gas manifold with all manner of gas bottles attached. I looked up the usual recipe, evacuated a bottle with a mechanical vacuum pump to "pretty low" pressure, and then added-in the gases I needed, carefully watching the partial pressure of each additional gas to make sure I got the mixture correct. The CO2 gas was a real bitch-kitty because the regulator kept freezing up. Slow and easy does it for that one! I must have done something right because the laser "lit up" just fine when power was applied and a 10.6 μm beam appeared at the output port. My only experience with CO2 lasers up to that point was with a 5 W Sylvania sealed-tube laser that used fixed Brewster windows and external cavity tuning mirrors. This was a plug-and-play laser that I used for several years without any problems.

After I worked on-loan for a while in Albuquerque, UDRI called me back to Dayton to work on other things. The Air Force was going nowhere with chemical lasers mounted in airplanes. Too hard to maintain, extremely toxic gasses produced during lasing, and very difficult to get enough energy on-target from a few kilometers distance from the target to ensure a definite "kill" shot. IMHO, what really killed this program (if it is indeed dead, and not just buried in some black budget somewhere) was the Navy research into electromagnetic rail-gun technology. "One pound to Jupiter" one of my old supervisors once told me. In other words, rail guns shoot heavy projectiles that have substantial momentum. I have heard it is like a Volkswagen bus, hitting you from nowhere at supersonic velocity. Hard to defend against momentum when it is coupled with a huge amount of kinetic energy. I am glad I got out of that race before someone demanded results, i.e., a battlefield weapon system. Guns and bullets will always trump a bright smile, even if sincere, any day. Add in biological, chemical, and nuclear players and who needs Star Wars laser weapons?

#### KILLERBUG

Mar 7, 2022
6
Wow...no need for any of that over here; I got out of 'defense' a few years back and don't miss it at all. Now I make a lot of art...and I use a laser to vaporize wood and acrylic in order to make that art...peaceful use of high power lasers to vaporize things.

#### hevans1944

##### Hop - AC8NS
Jun 21, 2012
4,792
There is always a peaceful as well as destructive prospect for any human endeavor. I do miss working with the "toys" modern weaponry can produce, but am simultaneously grateful that (so far) nothing really serious, like thermonuclear war, has resulted from that play.

My wife is an artist, painting and sculpture, being her main interests. So a few years ago I bought her a small kiln that is now in our garage waiting for me to build out a platform outside our house on which to place the kiln, plus some sort of "lean to" type shelter from the elements (rain mostly), and somehow run three 6 AWG cables from our electrical circuit breaker panel inside the garage, thorough a stucco and concrete block wall, to a weather-proof outside outlet the kiln electronics will plug into.

After that, I promised her I would find and hook up a 17.5 kV neon-sign transformer that would allow her to (safely I hope) create "lightning like" burn patterns in wood planks, soaked overnight in a brine solution to improve electrical conductivity. Of course a laser head controlled by an x-y CNC table could be programmed to burn similar-looking burn patterns with no danger of electrocution, but where is the excitement in that?

Replies
4
Views
2K
Replies
39
Views
3K
Replies
19
Views
1K
J
Replies
1
Views
1K
Gary Tait
G
Replies
1
Views
177