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Messages - madbean

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1
Wavelord doc is up.

2
Build Reports / Re: Snack Shack
« on: December 06, 2019, 10:43:59 AM »
I have a question about the orientation of the bc182 transistor.
The way the pads are marked (E-C-B) seems atypical.
I am still learning, so my question is whether this is a typo or should I really force the center pin (base) over to the furthest right pad?
Thanks

No need to force anything. The pinout of the BC182L is indeed ECB.

3
I had to re-upload the Runtime Error docs because the DC Jack was slightly off-center. If you downloaded it, delete that and get it again.
The Flunkee is up now.

I had the wonderful experience of accidentally overwriting the new 1590A template I had spent several hours on and then found out my automatic backups had not been working since Thanksgiving. So I lost half a day recreating the template. But, it's all good now!

4
Runtime Error doc is up. I should have a few more up tomorrow.

5
Few more days, definitely not weeks.

6
General Questions / Re: Quick question, Ohm's law!
« on: December 04, 2019, 08:50:28 AM »

Thanks a lot, that's very helpful.
I don't have any simulation software but I may try one soon.

I'm pretty sure the current output of a TC1044s chip is 20mA max. And downstream there's only one TL072.
So if W=RxI^2
W=22x0.02^2
W=0.0088

That seems so low though, is that normal? :D

That's simply the minimum wattage you could use. In real world practice you are going to use something that exceeds that and corresponds to the available specs from manufacturers (eg 1/8W, 1/4W).

I've found a good rule of thumb is 1/4W for 22R-100R and 1/2W for 10R.

You also want to consider the LP filter created by using a current limiting resistor and decoupling cap. For example, let's say you are using 100uF/100n combo for your PS filtering.

22R current limiting resistor:
f=1/(2*pi*R*C) = 1/(6.28*0.000022*100) = 72.4Hz for the 100uF cap
and, 72.4kHz for the 100n cap.
That's a decent amount of extra filtering on what may already be a well regulated and filtered 9v supply.

47R resistor:
33.9Hz and 33.9kHz resp.

So, as the resistance goes up, the freq. knee goes down obviously. And, as the resistance goes up the voltage drop across that resistor increases. The key is to find the right balance between proper filtering, minimal voltage drop and use the appropriate wattage so you part doesn't heat up as current is drawn through it. IOW, you don't need to re-invent the wheel every time you want to add some current limiting on your power. Just use this guideline:
  • High current draw requires higher wattage CLR.
  • Low current draw means you can use smaller wattage CLR and generally a smaller value.
  • Don't use a CLR too high as to cause too much of a voltage drop across it.

Also, you can look at using an inductor in place of a resistor. With those, you get a 2nd order LPF for free! Using the cap values I mentioned above a 1mH inductor gets you 2nd order LPF at 504Hz and 15.9kHz resp. So, a big improvement over just a resistor.

7
General Questions / Re: Silonex NSL 32sr3 Replacement
« on: December 02, 2019, 09:17:26 AM »
The R2 would probably be fine. It does not have as high of an off resistance as the R3 but I think it's close enough in this application. I forget what the difference is in response time between the three - that might be why he used the R3.

R1: 40R On, 500k Off
R2: 40R On, 5M Off
R3: 150R On, 25M Off

8
General Questions / Re: 9mmbuddies, why does it save "reversed"
« on: December 02, 2019, 06:59:54 AM »
Some of the 1590A projects have a breakout board where the pots are arranged in the typical triangle fashion. For those, the middle pot is reversed (goes on the bottom of the  PCB while the other two pots go on the top). For the individual breadbuddy ones it doesn't matter. You can solder them to either side of the PCB.

9
General Questions / Re: can i run the lowrider on 18v?
« on: November 30, 2019, 02:20:30 PM »
It should not cause any damage that I am aware of but I also can't say that it will provide any benefit.

10
General Questions / Re: total recall
« on: November 29, 2019, 07:47:38 PM »
what is the print on the back supposed to be? it kinda looks like a demonic shrek to me  :-\

It's kind of an 8-bit conversion of this from the movie (very disturbing but iconic nonetheless):



12
Open Discussion / Giving thanks.
« on: November 27, 2019, 07:54:13 PM »
Well, maybe it is cliched but nonetheless.

This thread is not about seeking praise. It's about giving it to those who deserve it - the ones that have helped you be who you are. It's an opportunity for you to give thanks to people that are special in your life. I will start.

Thanks to you. For being here, participating and making this community what it is. My job is to provide the framework, but you are the ones that make the community and make it special. I get so much inspiration from you guys it's kind of ridiculous. It makes me tear up a bit, even. Keep doing you, always.

Thanks to two of my mentors:
Terry Mattem: my guitar techer from 15-17 y.o. He taught me to play and even wrote a recommendation letter that helped me get into Berklee. I will always be indebted to him for his patience, inspiration and just being an awesome guy.
Faye Moskowitz: My middle school English teacher and counselor. She taught me that I needed to accept my own sense of self-worth but that did not entitle me to be an asshole. IOW, she taught me humility. It's been 35 years and I am still living that lesson.

My own family: whom always supported me even when I did not want to do so for myself.

Please contribute your own thanks if you feel the need. Trust me - it feels good to do it.

13
Open Discussion / Re: What are you playing? (games)
« on: November 26, 2019, 07:25:47 AM »
Ahh yeah, To the Moon has all of the feels.  There is another one by the same developers, called A Bird Story, which is similar.  I'd recommend that one too.

Me: Oh, that sounds cool I haven't played anything in a while.
- Looks up To the Moon on Steam.
"This game is in your library".

Oh, dear.

14
VFE Projects / Re: Choral Reef 14k3 resistors
« on: November 25, 2019, 09:38:23 PM »
The bigger thing is that the four resistors are very close in value. EHX used to do the same trick, the extra decimal means an extra degree of precision in production, so useful if a resistor has a really critical value.

In this case, they're being used as signal dividers, so the Mix knob will only truly be 50/50 in the middle if all 4 resistors are precisely the same value. If any of the 4 are off, an even split would be a little left or right of noon on the dial.

If the thought of that bothers you, then meter your resistors and use the 4 closest to one another. If you don't mind playing it by ear, then don't worry about it.

I wonder how much actual precision there is in terms of linearity across the physical wafer of these pots. IOW, is 50% of the turn actually accurate to 50% of the pot's resistance? I tend to think not too much! But, I've never actually looked into it.

15
VFE Projects / Re: Choral Reef 14k3 resistors
« on: November 25, 2019, 07:19:10 PM »
15k is perfectly fine.

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