Humble Electronics #011 - PAD - 234 Analog/Digital Trainer 01.3 (Summer 2023)

Now let's look at the clock and frequency generator outputs. The oscilloscope images were saved to a USB stick directly from the oscilloscope and transferred onto the computer. 

I should have made these connections neatly but I thought this was going to be a quick run through the maximums and minimums. I ended up spending quite some time changing the variables and observing the output. The signals were not very steady but I think they stayed within 5% tolerance and got more stable the longer the unit stayed on. I set the voltage at 5V by the oscilloscope but after I did the first set of outputs I realized that I did not do it correctly. I had set the max voltage 5V, not the peak to peak voltage so I did it again but with a Vpp of 5.04V. I placed a piece of tape over the knob so I wouldn't touch it while I varied the wave type.

 

The clock signal cannot be changed in amplitude but it does change depending on the frequency generator wave and the frequency. It's minimum voltage is 5.6V with a maximum at 7V. I don't think I'll need the clock generator as I could make one off of a microcontroller that will be more controllable. It will be included in these beginning slides.

 

I set the frequency generator so that the positive amplitude of the sine wave was at 2V but I did not consider the Vpp or the offset and ran through some changes. The wave is cycling at 899mHz which is the lowest usable frequency I could dial in. Vpp = 5.6V and it is not centered. The negative minimum is at -3.6V. I do not know what is causing the noise on my scope but it is likely a light bulb or my house is wired oddly (possibly not grounded properly). The noise is always there regardless of the device under test.

 

 I left all the settings the same and I changed to the square wave.

 

The 'scope is reading a voltage of 7.8Vpp at 909mHz. The clock voltage had gone up to 6Vpp. I then changed the wave to the triangle wave.

The voltage has gone down to 6.6Vpp and the frequency to 893mHz.

I reset the generator for 5.04Vpp and a sine wave at the lowest usable frequency I could which was 902mHz. I switched through the square and triangle wave and I got similar results, higher voltage and frequency, 7.44Vpp and 896mHz on the square wave and 6.16Vpp and 912mHz on the triangle wave.

 

Then I switched to the highest frequency available. Like before it varied between the different wave forms. The maximum frequency was steady at 114kHz but there were distortions in the signal. The square wave looked more like a saw tooth wave and the triangle wave looked like a sine wave.

I missed capturing the 5.04Vpp sine wave at  high frequency so I went back and did it a few days later. I reset the generator for the lowest frequency sine wave at 5Vpp and then raised it to the highest frequency. 

The voltage went down to 1.94Vpp at 114kHz. The thin spikes off the wave decreased significantly as the unit warmed up.

At the same session, a few days later that the original, I reset the frequency to around 100kHz and tested the maximum voltage for each wave form. The sine wave had a maximum voltage of 5.20Vpp. The square wave had a maximum voltage of 18.6Vpp but looked like a discontinuous saw-tooth wave. The triangle wave had a maximum voltage of 11.8Vpp and did not have a sharp peak.

When I adjusted the amplitude, there was an audible crackling/static sound coming from the unit. I don't think I'll run it so high in amplitude until I can open it and see if its OK. The rest of the captures are from the first session.

 I switched back to the sine wave and changed the amplitude to the max available and measured 13Vpp with the minimum frequency of 950mHz.

I then tried to find a usable square wave. I adjusted the frequency on the square wave until it looked at least halfway square. This occurred around 56.2kHz and 8.2Vpp. The rise time is 2.25uS but it still looks relatively long.

All the above readings do not have the offset adjusted. I went through the same values again and adjusted the offset of the 5Vpp sine wave only. The offset and the Vpp changed as I switched through the different wave forms like before.

In conclusion, (I sound like a lab report 🙄) The frequency generator on this device needs to be set and checked up on with an oscilloscope. It does need some time to warm up until the sine waveform is smooth. It varies in voltage and offset which will change results if the waveform is changed. The frequency generator should probably be connected to a circuit so that it can be easily removed, reset and measured apart from the circuit, and then reattached, if needed. I think it will work fine for many basic function generator operations under 100kHz.

I'm going to take a small break from posting. Real life has thrown a wrench in the works for a short time. I think this is going to happen often in the next year. This blog is one of the first things taking a back seat when it gets unpredictable here. I will try to make at least one post a week and it may still be possible, depending on how in depth it is, but it is a low priority for me. I've got a few projects I'm using the PAD-234 for. One is to measure inductors and the second and third are my WLED projects, which I will talk about first before getting into what I'm trying to do with it. I'm looking forward to those and want to get cracking on them. My Laser Cutter posts will cover some of the things I made quickly and will still be alternated with the electronics posts. In the meantime...

Happy Making!

Michelle