Finally, after acquiring this oscilloscope almost a year ago I managed to test it out the other day. Before firing it up I took the side panels off and carefully dusted off the internal components with an air hose. With safety glasses on I plugged it in, stood back and flipped the switch - all good. While it warmed up I read over the Philips manual I found online for a different model that is within the same time period (that's the best I could do). Not sure how well calibrated this unit is but I decided to play around and see what it could do with a basic circuit. I put together a simple bridge rectifier circuit and applied about 5 VAC using a Variac. Placed the probe across L1 to ground and then across the capacitor and got predictable sine waves. Not going into business with this scope but it's a starting point. Here's some images:
Congrats on getting it up and running! It looks like you only have a half wave rectifier circuit going there, and either low capacitance or low resistance. One rule of thumb for input filters is that your RC Time Constant should be around 10 times your input period. For 60Hz, we would divide 83(full wave) or 167(half wave) mS by the load resistance, to get the desired filter C in Farads. You could experiment with different calculated values and observe your ripple amplitude. Can you imagine what the output of your LM317 or LM350 circuit would look like with this as your input??? Joe
Back in the olden days we used an inductor and a capacitor for a filter. Then they just make the "bulk" voltage a bit higher than what they need and clip the ripple off with a voltage regulator. Now days they use SMPS designs instead of the old transformer supply and ripple is not as big a problem because of the frequency.
Not sure where I'm headed with this new found hobby but I find it all very interesting. Recently I built a simple function generator circuit to play with. First time I ever used a 555 timer. As most of you likely know there is a lot of options for a homemade function generators. Not sure if I picked a good one. If anyone knows of circuit that is proven I would appreciate a link to the site or a diagram if possible. Thank-you.
The 555 timer and its follow-ons have got to be some of the most useful ICs ever invented. The 556 is a dual and the 558 is a quad. The TLC and 7555 are low power, CMOS versions of the same. You will learn a lot playing with them. 2 resistors and a cap, get you an astable multivibrator.(>50% duty cycle) Adding a diode gets you any duty cycle that you want. Feeding a variable voltage to the control voltage pin gives you basic PWM capability. I first used one to build a wiper delay for my Chevelle back in the 70s. I have 2 going into my B-17 now, to pulse 100CD LEDs as strobes, and to brighten and dim to appear like a rotating beacon. There are actual function generator chips out there, but most have been discontinued. I remember that Harris and Exar had them. Digi-Key only shows a couple and they show zero stock. I just showed a friend at work a circuit that spanned <2% to >99% duty cycle, while staying at roughly the same frequency. I did it by connecting the wiper of a linear, multi-turn pot to Pin 7, with each end going through low value fixed Rs to Pin 2,6 and V+. You use the fixed Rs because you really don't want to short your Discharge Pin 7 to V+ OR the Trigger(2) or Threshold(6) pins. Adding a plain small signal diode (1N400x, 1N914, 1N4148,...) Cathode to 2,6, Anode to 7, gets you the <50% duty cycle. If you were to substitute a linear, dual pot for the 2 fixed R's, it would be a frequency adjustment. If you then added a rotary switch to change capacitors between 2,6 and ground, you would have a range switch. I attached a PDF that I generated to help fellow RC club members, strobe their LEDs. Joe
That's a great deal Greg! "Estimated Delivery Date: Aug. 12 - 28 when you choose Standard at checkout." I just don't understand how any standard shipment will take that long. They must be building them to order in China and walking them to the container ship. Here is MPJA's version. http://www.mpja.com/Pulse-Generator-Board-Adjustable/productinfo/31070%20MI Of course, these all should be called rectangular wave or pulse generators, and not square wave generators. You can always double the frequency and follow the output with a JK flip-flop like a CD4027 if you need square waves. Joe
That is exactly what buying stuff from China is like. Shipping is "free" but it takes 5 weeks. The ones I ordered came in faster but I just got lucky on the ship.
BTW this comes US mail locally. It is all part of that deal post offices have around the world. The receiving post office has to deliver the package free (or almost free) as long as the postage was paid in the sending country. Most countries whack their shippers pretty hard. China makes it almost free on their end. That is how they can offer free shipping, it is free for them. I can often buy something (material and shipping), shipped from China and dropped off at the Long Beach post office, cheaper than a USPS package from Long Beach to here costs.