Omni

The link provided below is a high quality mask for soldering, view the link description. "Workplace applications include welding, brazing, soldering etc..." http://filtera.stores.yahoo.net/3mmod82n95pa.html Today, it is also advisable to simple remove the solder fumes via an extractor, the latter would also eliminate the aspect of a mask which can become uncomfortable. Furthermore, take the time to search the internet for price along with features that you will desire. http://www.sentryair.com/solder%20fume.htm http://www.sentryair.com/solder-sentry.htm http://www.howardelectronics.com/xytronic/426dlx.html http://www.elexp.com/sdr_6dlx.htm http://www.engineeringlab.com/fumeextractor.html http://www.mcminone.com/product.asp?catalog_name=MCMProducts&product_id=21-7960 -Omni

Free service manuals along with user manuals can be noted at the below sites. Additionally, if you can be more specific: make/model i am sure the forum group can provide a better direction etc... http://www.eserviceinfo.com/ http://bama.edebris.com/manuals/ -Omni

0-30VDC Stabilized pictures. The supply was completed around 6 months ago, what an excellent project; a true performer! Hopefully, i can post some pictures showing the enclosure and digital display module; magnificent original design! In the past i really enjoyed taking digital pictures, anymore i lost my interest for digital photography.

The original design when properly built will work without any problems. I favor the latter supply over my BK supplies along with an Hp supply. Although, the BK & Hp can provide much more current, the simplicity of the 0-30V bench supply is far more useful for my purpose. Added note: as i stated in a prior post/thread it can be a teaser since it has a few very unique features. The ripple at 30V is very respectful, well within the aspect of the circuit design. I have yet to notice any problems under full load at higher voltages. Additionally, when building the supply make sure to board space any component that will generate heat; power resistors, diodes, zener's etc... The 2N2219 along with the output transistor require the proper heat sink. Obviously, with any power supply that will be used to maintain high current over an extended period of time should be carefully thermally sized. Adequate clearance must be provided for the PT, use a high quality military grade or similar; do not purchase an inexpensive one from a surplus house... Search the internet for a quality transformer, expect to pay around $45.00 - $60.00 (USA currency) Furthermore, if the output drive transistor is mounted within the case a ventilated design along with a quality DC fan should be used. Remember, fan noise can be reduced considerable by lowering the fan voltage, a small/simple DC fan control circuit consisting of a voltage divider network along with a transistor is sufficient. One could also use a darlington (TIP120) if fan current is above average.

I remember at PENN a variety of students that always wanted me to provide an outline concerning a completed project; always looking for the answers without making any attempt on their own. :'( I would kindly state the below in a very respectful manner: The only way you will learn the questions you are asking is to pull the legs one by one from the centipede. When you have completed the above you will gain a much better understanding. :) I truly honor the individual that has presented this project, PCB artwork along with a brief functionality is so difficult to find today! I view far too many circuits/projects on the internet that are continual copies of a basic format. Today, we must learn how to work outside the box! -Omni :)

A feedback path can also be viewed as a dynamic feedback. Ugh, different executions are performed throughout the circuit when required, bias shunting etc... Including, certain parameters (power, voltage or current), establishing set points occur in a much more controlled level when using an op-amp design. Enroll in a class (semester) concerning "Advanced Power supply design and circuit application", the latter is usually available at any University.

One has to understand how a precision op-amp output biasing is performed before understanding the advanced principles of the stabilized output. Within the circuit are many feedback paths that form/conduct the Vout in a very controlled manner. Additionally, view the unique shunting path that is performed, the original circuit is a marvel! The superb design of the DC clamp upon shut-off is magnificent. However, it could never be easily performed on a basic 78xx series regulator using the design implemented on the 0-30V supply. Although, there is always a work around that will perform a similar function using a more passive characteristic. I provided the pic/link, one could also use an SCR in place of the relay but the region of operation can become subjective, using a basic high-quality sealed relay will remove all aspects of the subjective content. One could tap from the P/S bridge but an excessive capacitance is noted that would generally require a zener/resistor to the relay. Using an isolated bridge with very minimal capacitance is the key since a relay is a basic coil, non-silicon device. However, make sure to select the relay coil for minimal current consumption; 30mA etc... The above can also be replaced with a relay on the AC side but i do not like the idea of RAW AC engaging a relay. Although, arc supression can be be implemented it is far easier to use the secondary side to eliminate the large contact potential. Please, understand higher current devices (project circuit) would cater to using an SCR but for low current applications like the timer circuit the 12VDC supply is powering (300mA) a relay is perfect. Far too many designers reduce the secondary capacitive filtering along with installing a fixed load to pull the output decay rapidly, the latter causes excessive component wear along with increased loading on the P/S; heat generated is high!

The original design will operate perfectly, i have completely tested the 0-30V supply and feel it is one of the best i have ever used. I fabricated my own PCB using the internet supplied artwork along with PnP. The only addition i added was a digital voltage & current meter; link provided. http://www.hobbytron.com/UK203.html I ordered all the parts for the supply from Futurlec, their prices are excellent! The enclosure is a ventilated Bud (champion series). http://www.budind.com/pdf/hb11202.pdf Furthermore, the green (stock) 7-segment LEDs were replaced with Red since i fabricated the front panel enclosure out of dark red plexiglass. However, you could also use a dark green plexiglass and use the stock LEDs. (the Digital I & V meter uses stock green/yellow LEDs) Plexiglass can be purchased in very small sizes from ebay, be carefuly when drilling, do not attempt to immediately drill a large hole (.25) above, start very small and work your way up. Plexi has a tendency to grab the bit and a crack will easily occur (drill very slow), no pressure! I hope i can get some time to post a few pics; perhaps this weekend.

Actually, if i spend the time i can get the posted pic (12VDC) circuit to simulate the clamp as designed on the 0-30V stabilized supply. I was hoping someone had already designed a working model... Your theory would not work in my situation since the LM317 would still produce a decay when power is turned-off, the timer circuit i designed will only draw 200mA of current when power is applied. The latter circuit will also operate slightly below 4V at which time the extremely low current relay disengages. Circuit current consumtion in today's digital designs are very low. When a worst case scenario is applied such as power-on/off/on applied at both AC and DC levels digital design can take on a whole new meaning! Although, i thank you for your concern. -Omni

"very quickly" cannot be measured... I would like to duplicate this feature on the link below. My digital timer module will not work properly unless i have the "very quickly" feature! The below link is the supply i am trying to use for a timer circuit but the decay on the output is creating havoc, i tried a 50 ohm shunt across the output it does help but not flawless like the 0-30VDC stabilized supply when adjusted to 12V. If possible, please be specific as to how it may be performed. Additionally, i understand if it is not possible etc... Any help would be appreciated.

Listen very carefully, The 0-30 Vdc stabilized supply is a very advanced design. Truthfully, it is a marvel but can also become a problem. Example: In the event you plan to use this supply on your bench to test homebrew digital circuits "BEWARE". The advanced shut-off is the most amazing i have ever noted. Example: Let's say for instance you designed a multi-timer circuit using the 555 - 556 group of timers. The latter timer circuit eventually is used to light a few LEDs along with activating a relay etc... Powering and testing the timer project you are using the 0-30V stabilized supply. However, you plan to make an on-board constant 12V supply for the timer project. You test the timer and every aspect will work perfectly, you try a fast-on, fast-off then back again; multiple times in extremely fast order. Additionally, while the 0-30V is powering the timer project you pull the AC plug out of the wall then immediately push it back into the wall. Regardless, as to what you try your timer project will time-out and work perfectly! Next, after you design the PCB for the timer project you build a small +12VDC supply onboard to power the timer circuit; basic supply. Wow, will you be let down... All of a sudden when you try a fast on/off/on cycle the timer does not respond correctly, relay is engaging immediately, LEDs are flashing out of order etc... The basic 12V supply cannot perform like your test bench 0-30V supply, you then try to load the 12V PCB mounted project supply to clamp the output voltage to zero but the minimal delay is still a problem; im talking strapping a 50ohm resistor across the 12V PCB supply is too slow! The 0-30V is the ultimate supply but in real-world situations it is too perfect, unless you plan to buy or build another just to place in your project you may find the latter supply more of a tease than anything! Trust me, i found out the hard way! -Omni ???