That is much better, except I would put a ceramic 100nF AND a 10uF+ electrolytic on BOTH sides of the prop.
So on the side you have the ceramic, also add an electrolytic.
On the side you have the electrolytic, add the ceramic.
Some overshoot is normal.
greitz said...
Bill Henning said...
Please put a 100nF ceramic, and at least 10uF (up to 33uF) electrolytic cap on each side of the propeller, between the propeller's Vcc and Vss pins.
Did I place the caps in the correct places? I wasn't sure if you meant, one 100nF ceramic on one side and one 10 to 33uF electrolytic on the other side, or two on each side.
Is there a schematic that I can follow that shows the capacitors? I have been using the 'Typical Connection Diagram'.
I also added a LM2937 3.3V regulator. Thanks for the tip, previously I fried one of my props (first time) when I accidentally raised the voltage to about 8V.
Cluso99 said...
I missed the overclocking bit. I just would not overclock a breadboard. And you MUST have 0.1uF decoupling ceramics at both sides of the prop power/ground pins with short leads. A 10uF tantalum on each would not go amiss either.
This setup is using the standard 5MHz crystal.
Overall, it looks better but still overshoots by about a volt.
I also tried it with the 6.25MHz Crystal and it looks about the same. Maybe slightly worse ripple, but barely noticeable.
Thanks again,
graham
Edited to add test with 6.25MHz crystal and voltage regulator
A square wave is actually an infinite series of sine wave harmonics added together. Scope probes, power leads, IC internals, and several other factors can create parasitic filters that can emphasize (tune) and de-emphasize (de-tune) some of the harmonic components associated within the square wave.
"...If the system is overdamped, then the waveform may never actually reach the theoretical high and low levels, and if the system is underdamped, it will oscillate about the high and low levels before settling down..." <- Which is what we see.
...In this particular situation it is better to be under damped simply because you can add resistance to 'dampen' or attenuate the signal, where as being over damped your signal has an inadequate amount of drive strength from the source to begin with.
See the attached images... 'P0.jpg' is measured directly off of P0 where as 'P0 with 100 Ohms.jpg' has a 100 Ohm series resistor off of P0.
Also is the attached program used to generate the signal on P0.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔ Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 3/2/2010 5:33:37 PM GMT
Ignorance is bliss and a little bit of ringing never hurt anyone, or so said Quasimodo.
Nice synthesis Peter. So I guess 2+2=5 rings.
hover1 said...
It looks like carbon is you friend!
Is that "carbon offset"?
Of course too much of anything is bad for you.
@grietz,
It may not matter, but your probe calibration signal should be a nice square-wave.
Use the probe trim adjust to make it square if possible.
Also, make sure your probe is set to 10x for best measurements.
Comments
Those spikes are probably already being snipped off by the Prop's protection diodes.
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Style and grace : Nil point
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Leon Heller
Amateur radio callsign: G1HSM
So on the side you have the ceramic, also add an electrolytic.
On the side you have the electrolytic, add the ceramic.
Some overshoot is normal.
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www.mikronauts.com E-mail: mikronauts _at_ gmail _dot_ com 5.0" VGA LCD in stock!
Morpheus dual Prop SBC w/ 512KB kit $119.95, Mem+2MB memory/IO kit $89.95, both kits $189.95 SerPlug $9.95
Propteus and Proteus for Propeller prototyping 6.250MHz custom Crystals run Propellers at 100MHz
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I should have looked at this closer....
A square wave is actually an infinite series of sine wave harmonics added together. Scope probes, power leads, IC internals, and several other factors can create parasitic filters that can emphasize (tune) and de-emphasize (de-tune) some of the harmonic components associated within the square wave.
en.wikipedia.org/wiki/Square_wave
"...If the system is overdamped, then the waveform may never actually reach the theoretical high and low levels, and if the system is underdamped, it will oscillate about the high and low levels before settling down..." <- Which is what we see.
en.wikipedia.org/wiki/Damping
...In this particular situation it is better to be under damped simply because you can add resistance to 'dampen' or attenuate the signal, where as being over damped your signal has an inadequate amount of drive strength from the source to begin with.
See the attached images... 'P0.jpg' is measured directly off of P0 where as 'P0 with 100 Ohms.jpg' has a 100 Ohm series resistor off of P0.
Also is the attached program used to generate the signal on P0.
▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Beau Schwabe
IC Layout Engineer
Parallax, Inc.
Post Edited (Beau Schwabe (Parallax)) : 3/2/2010 5:33:37 PM GMT
Is that "carbon offset"?
Jim
Of course too much of anything is bad for you.
@grietz,
It may not matter, but your probe calibration signal should be a nice square-wave.
Use the probe trim adjust to make it square if possible.
Also, make sure your probe is set to 10x for best measurements.
Post Edited (jazzed) : 3/2/2010 7:12:35 PM GMT