Recent Posts

1

Beginners / Re: LC filtering for combined Vref/VDD of ADC

« Last post by pcprogrammer on Today at 06:30:49 am »

Better way of doing this kind of thing is to create separate supplies for both analog and digital. Can be done with ferrite beads, resistors and capacitors coming of of the same supply voltage. By matching the supply voltage of both the digital and analog parts by trimming the series resistors there is little risk in exceeding maximum input voltages. The ADC works down to 2.7V and most likely the MCU you are using will also allow for some deviation of the supply voltage.

Also using multiple different value capacitors in the decoupling helps in reducing the noise. A friend of mine who is much more of an expert advised me to use parallel 100nF, 10nF and 1nF capacitors before and after the ferrite bead, and then the series resistor followed by a larger capacitor like 10uF. Then still add the 100nF decoupling capacitor advised for most IC's. See page 18 of the MCP3202 datasheet.

The different value capacitors seem to have different responses at different frequencies and therefore do a better job in filtering a wider spectrum, so I'm told.

2

Repair / Re: Tektronix 2225 vertical display problem

« Last post by MathWizard on Today at 06:28:54 am »

Hi there, do you have another scope, or signal tracer ? Here's a service manual with schematic's. I'd try and trace the signal into the attenuation/pre-amp section, and then the main vertical pre-amp and driver section.

I have no idea what this site is, but the 216page 14MB pdf is too big to upload.
http://bee.mif.pg.gda.pl/ciasteczkowypotwor/Tek/2225%20SM.pdf

3

Projects, Designs, and Technical Stuff / Practically smallest SMD size for assembly run of 1 to 100 pieces by PCBWay etc

« Last post by Wilson__ on Today at 06:26:15 am »

What is practically smallest SMD size, for making PCB and component assembly, for 1 to 100 pieces by PCBWay etc. for these components:

Resistor (signal, no heat rating required)
Power line by pass capacitor
LED as visual indicators, charging and done

Do they x-ray inspect board with leadless chips, 1 x 1 mm and 2 x 2 mm, and masking sure there is no assembly error, no solder or shorted solder?  They need to be correct as it is too small for me to debug or re-solder.

Many thanks

4

Programming / Re: Angle wrapping in code, "easy" problem, need to double check

« Last post by Siwastaja on Today at 06:24:07 am »

For angles that need to wrap, I'd suggest, instead of degrees, use 65536/360 deg (~ 0.005deg) as your base unit. (Or 2^32/360 if you need more resolution, or 256/360 if that suffices!). This way, wrap around always Just Works implicitly - and efficiently, in CPU registers directly (either with zero cost, or in worst case, requiring a single instruction to mask out bits):

uint16_t angle = ...;
uint16_t angle_plus_90deg = angle + 16384; // implicit correct wrapping guaranteed by C standard
...

You can further just choose to cast into signed type (int16_t) to interpret the angle between -180 .. +180 deg.

Only convert to degrees when interfacing with human, in UI.

In C, this is all standard; unsigned arithmetics are guaranteed to provide modulus operation when the result overflows, so if you ever came across with an oddball CPU architecture which does not do this on machine level, then the C compiler for that machine would still emit the correct instructions, and as such, the solution is portable.

5

Beginners / Re: Automatic golf ball dispenser

« Last post by BTO on Today at 06:14:52 am »

Ok so I simple need to power sources

No.. you SIMPLY need TWO power sources 
Yes that's correct, You're very close, Throw in a dedicated power source for the solenoid and test it.
Let me know how it goes

Again this is where you can try using that dual power supply board (MB102) that you bought, (Depending on the requirements of the Solenoid)

6

Beginners / Re: Automatic golf ball dispenser

« Last post by Maclarkson on Today at 06:09:50 am »

Ok so I simple need to power sources

7

FPGA / Re: Analog video output with FPGA ?

« Last post by Jaunedeau on Today at 06:03:16 am »

Didn't you say DAC, not ADC?

The idea is to have both and ADC and a DAC, and use the ADC to calibrate the DAC and build a lookup table to correct the DAC errors. I've found a post about this idea ( https://www.eevblog.com/forum/projects/r-2r-ladder-dac-calibration-what-do-you-think/ ) and when you see the first oscilloscop capture, it seems possible to make a calibration table and get a good 14bit adc from this 16bit R2R adc after calibration.
My case is a bit different : I need 8bit not 16, but about 30Msps not 44ksps. Also since my input is discrete (e.g. the atari 2600 has a 128 colors palette), I could build a calibration table for the 128 RGB triplets instead of three calibration tables of 256 individual R, G and B and compensate for the crosstalk.

I am a software developer, only learning electronics as a hobby, I have no intuition of if this could be a good solution (to the problem of video ADCs eventually no longer be available in a few years, and cost reduction because cost reduced projects are more fun to me).

8

Repair / Re: Mig welder wire feeder controller board not working

« Last post by TERRA Operative on Today at 06:00:17 am »

there has got to be a better filter then a foam ear plug. maybe a fine nylon brush?

its such a dodgy construction worker hack

I don't like it because theoretically something can get stuck in the foam and scratch up the wire, and it can soak up grease and smear it on etc. I feel like a nylon brush would brush off debris and result in cleaner wire

there must be a more professional engineering solution to this using better hardware

The 'official' way is a lightly oiled felt 'slug' held on with a metal clip.
https://www.google.com/search?q=mig+wire+cleaner&udm=2

Thank you so much.  I did not expect this sort of information to be available.  When I bought this welder new I did not even get a manual with it.

I think i should be able to do something now, probably let the magic smoke out somewhere.

The benefit of buying a quality brand instead of a cheap Chinese no-name import.

And I archived all the manuals from when I was in the welding and cutting equipment repair game.

9

Test Equipment / Re: TinySA Ultra launched

« Last post by erikka on Today at 05:58:50 am »

The tinySA does not do a continuous sweep but sweeps in discrete steps with possible silence in between. Set the scan speed slow and you will see the step

10

General Technical Chat / Re: The strange case of phase angles

« Last post by sicco on Today at 05:49:43 am »

The voltage source has an output impedance of zero ohms. It thus dictates a voltage on both the R, the L and the C. No matter what the values are for R, L or C. So no way that L, C, or R can ‘see’ each-other and form a LC resonator or so.
The phase angle from voltage to current through each component leg is zero for R, 90 and -90 for L and C. The current from the source is the sum of I_R, I_C and I_R. So subtract L and C currents because they are 180 deg apart. Then atan the imag and real. So something like atan((I_L - I_C) /I_R) for the phase difference from V_source to I_source.