| Electronics > Beginners |
| My purchase list for my new lab -- budget $1000+, thoughts? |
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| AnyNameWillDo:
--- Quote from: rhb on July 22, 2018, 07:07:19 pm ---In fact the OP would be well advised to get that and an older edition of "Electronic Principles" by Malvino or Malvino and Baker. You do *not* need a current edition unless you're taking a class which is going to assign a particular problem. Malvino is a PHD engineer who took to writing trade school textbooks. They are beautifully written and he actually builds all the circuits in the book to verify that he got them correct. The current edition is over $200 which is insane. But it has the virtue of knocking down the price of the previous edition. --- End quote --- If you are referring to https://www.amazon.com/Electronic-Principles-Albert-Paul-Malvino/dp/0073373885/ I did purchase this a couple days ago (along with several others) |
| rstofer:
--- Quote from: rhb on July 22, 2018, 07:07:19 pm --- --- Quote from: mathsquid on July 22, 2018, 05:35:07 pm --- --- Quote from: rhb on July 21, 2018, 11:45:04 pm ---Mains powered equipment is not dangerous if it is unplugged. --- End quote --- Is that true of a switch-mode power supply? --- End quote --- As noted, in either instance you do need to have the sense to discharge the capacitors before touching the terminals. For pete's sake, this is an electronics forum. People are supposed to either understand electronics and electricity or want to learn it. I very much doubt that there are many 5 year olds with $1000 to spend on an electronics lab. --- End quote --- Maybe the point is that a person doesn't know what they don't know. If they were to discharge the capacitor, how to do it safely? Short it with a screwdriver? Probably not! OK, then what size resistor? What is the maximum voltage to expect? How long will it take to discharge? How much heat is dissipated in the resistor? And so on... It's one thing to play on the bench with low energy sources. It's quite another to be messing around with higher voltages and lots stored energy. Yes, eventually, all of the questions are answered and the process is quite safe. But it is not the kind of thing that needs to happen day one. |
| rhb:
--- Quote from: rstofer on July 22, 2018, 07:55:26 pm ---Maybe the point is that a person doesn't know what they don't know. If they were to discharge the capacitor, how to do it safely? Short it with a screwdriver? Probably not! --- End quote --- WTF???? First of all, the shock hazard from a capacitor charged to 35-50 V is non-existent. There are no capacitors on the mains side of a linear supply. We are *not* discussing working on the HV supply for an oscilloscope CRT. You *don't* use a good screwdriver as, if there is a significant charge, you'll damage the screwdriver. I have a junk screw driver with plastic handle that I modified to form a 90 degree pointed tool to reach the addressing DIP switches on the Emulex SCSI-ESDI cards used in Sun shoe boxes. That's what I use. If for some reason I need to use a good screwdriver I just make sure I don't let the discharge hit the tip. Resistors are for bleeders designed into the circuit, not for service safety precautions. If you do a lot of work on HV PSUs you have a screwdriver with an alligator clip that you connect to ground and the first thing you do after opening the cabinet is discharge all the capacitors. For that a resistor is a good idea so that you don't damage the capacitor terminals if they have push on connections. There's a very basic concept here. Before you go to do something with which you have little or no recent experience, you get a book and read it first. There is a *lot* of stuff I did 30-40 years ago that I wouldn't consider doing today without sitting down and reading up on the subject first. And I certainly would not trust the internet or YouTube with videos where people pour cast iron on concrete floors and similar completely insane stunts. Like the guy who had his girlfriend shoot him with a .50 Desert Eagle with a thick book as "protection". I *do* know what I don't know. That is the single most important thing to learn. That makes further learning possible. Novices would have a lot easier time if people explained "what and how" rather than repeating nanny state "don'ts". |
| ez24:
Be sure to check out Tequipment discounts for members, I forgot the secret code. But you can get the 10% 6% by calling them and tell them you are a forum member Also this https://www.eevblog.com/forum/beginners/from-no-parts-to-decent-stockpile-best-approach/msg734584/#msg734584 |
| jrd:
Your test equipment needs are really driven by your interests. I was once a tube audio builder who later in life got interested in Ham Radio. As a result, my test equipment minimum needs changed - moving from a PC plugin oscilloscope, audio card and cheap multimeter over to purchasing a real 200 MHz two-channel DSO, an LCR meter and yes Function Generator. None of my intended original "investments" lasted long. 1. Not sure how valuable a 4 channel scope is for you. Dont forget a 50 MHz DSO at 4 channels = 50 / 4 = 12.5MHz max sample rate if all channels are enabled. This means if you intend to use all 4 channels at the same time for Digital Work, its going to be for very slow 1980s type TTL and CMOS speed circuits. You might be better served by two channels at 100 or 200 MHz for alittle less money, and a purchase of some nice high impedance scope probes to go with the instrument. 2. In this day and age of I2C and SPI tidbits, a scope that has built in decode of these bus traffic types is *VERY* useful to have handy for troubleshooting and repairing things around the house. Rigol and Siglent scopes have these. 3. In lieu of an LCR meter, you can use the scope to accurately perform these measurements. You dont need a Function Generator, but you would need some accurate source of frequency. Learning to use the scope to perform these basic measurements (and calculations) reinforces good habits. 4. You need a good set of probe accessories for both your meter and scope. If you are sticking to 24V or less, then a 1x Scope Probe is fine. But you will need Pomona grabbers, SMD tweezer grips and a mixture of snort and wide probe tips for both your meter and scope probe. You should carefully learn about oscope connection discipline with respect to ground and making floating measurements to protect your scope from death. Very important early habits to master! 5. A Current Limited Bipolar Supply (+/- 15V) prevents you from blowing up parts, or suffering fingertip burns, when you breadboard. It's incredibly easy to screw something up and get an op-amp to run off to rails, or dump current through a transistor. The current limiting power supply will let you make mistakes without blowing up parts along the way. Some parts are expensive, you will run into $15 op-amps and $8 JFETs that you certainly wont want to loose. For Tube Audio work - I have a Heathkit IP17, that gives me 0-400VDC to 100mA to work with ; more than enough to prototype or troubleshoot a single audio channel be it pre-amp or power amp. Also, a 10x Tektronix probe. The scope probe has nearly never gone to a Plate terminal,connection, I measure at the cathode or the cool side of the coupling capacitor. Ultimately, tube audio work needs a Differential Probe to do it right, but it can be done wiht a x10 probe with extreme vigilance taken to ground reference! -- Jim |
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