| Author |
Message |
julianw
Joined: Jul 30, 2007
Posts: 78
Location: UK
|
 Posted: Wed Oct 31, 2007 11:36 am Post subject:
22 ohm resistor or ferrite bead? Which one is best?
Subject description: Does it matter? |
  |
|
Hi Everybody,
I read that ferrite beads reduce electrical noise and 22R resistors can be used in their place, Rykhaard said:
| Quote: | | I myself have been using a 22 ohm resistor for +V and -V power supply inputs for about 18 months now. They have saved me from blowing MANY fuses, in that time |
So it seems that 22 ohm resistors are also useful as overcurrent protection devices too, but are they as effective at reducing noise as the ferrite beads  |
|
|
Back to top
|
|
 |
fonik
Joined: Jun 07, 2006
Posts: 3950
Location: Germany
Audio files: 23
|
| Posted: Wed Oct 31, 2007 1:19 pm Post subject:
|
|
|
indeed. and i am using them even on the breadboard. when at least one of them emits magic smoke i know that there must be something wrong 
_________________
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source |
|
|
Back to top
|
|
|
shawn
Joined: Dec 13, 2005
Posts: 209
Location: savannah
|
| Posted: Wed Oct 31, 2007 1:24 pm Post subject:
|
|
|
| I just use 22R resistors with my modules. Ken Stone suggests using either a ferrite bead or 22r resistor but I'm not sure if there are any real drastic advantages of using one over the other. |
|
|
Back to top
|
|
|
blue hell
Site Admin
Joined: Apr 03, 2004
Posts: 24582
Location: The Netherlands, Enschede
Audio files: 308
G2 patch files: 320
|
| Posted: Wed Oct 31, 2007 2:30 pm Post subject:
|
|
|
The ferrites should give better suppression of unwanted signals both going into and coming out of the supply lines. The resistors will give better protection. I can imagine using resistors initially and when all works like it should replace 'm by the ferrites.
_________________
Jan
also .. could someone please turn down the thermostat a bit.
 |
|
|
Back to top
|
|
|
goldenechos
Joined: Jun 06, 2007
Posts: 201
Location: Marshall, NC
Audio files: 1
|
| Posted: Wed Oct 31, 2007 2:38 pm Post subject:
|
|
|
The 22R gives an amazing amont of protection. My power supply is of the cobbled together type, I hooked up the leads incorrectly when I fired up my BiNTic filter a cople weeks ago.
Not an op-amp on that board was damaged! I replaced the 2 22 ohm resistors, connected the power correctly, and everything was peachy.
Tony |
|
|
Back to top
|
|
|
Danno Gee Ray
Joined: Sep 25, 2005
Posts: 1351
Location: Telford, PA USA
|
| Posted: Wed Oct 31, 2007 2:40 pm Post subject:
|
|
|
Would anyone care to post a diagram of how these beads or resistors are connected?
I would find it educational.
Thanks. |
|
|
Back to top
|
|
|
tomcat
Joined: Oct 14, 2005
Posts: 141
Location: earth
|
| Posted: Wed Oct 31, 2007 3:47 pm Post subject:
|
|
|
| In Serie, like a fuse. |
|
|
Back to top
|
|
|
shawn
Joined: Dec 13, 2005
Posts: 209
Location: savannah
|
| Posted: Wed Oct 31, 2007 3:54 pm Post subject:
|
|
|
| Plus them in between your power and the rest of the board. |
|
|
Back to top
|
|
|
TheAncientOne
Joined: Dec 26, 2006
Posts: 144
Location: United Kingdom
|
| Posted: Wed Oct 31, 2007 7:52 pm Post subject:
|
|
|
You can have both: if the PCB has limited space, stand the resistor upright, and put the ferrite over the long 'bent down' lead.
Used in few instrumentation modules, though I've yet to try it in a synth.
_________________
Mike |
|
|
Back to top
|
|
|
Rykhaard
Joined: Sep 02, 2007
Posts: 1290
Location: Canada
|
| Posted: Wed Oct 31, 2007 9:42 pm Post subject:
|
|
|
This pic shows my now standard layout, since converting to 4 pin Molex connectors, a couple of months ago. (The 0.156" spacing ones).
As I'd said elsewhere earlier - the recommended 22R 1/4 watt resistors have saved me untold amounts of stuff being damaged. (Heh. Due to my own 'duhhhhh' the Tom Bugs Pattern Generator cost me SEVEN x 22R resistors.  )
I do like the recommendation though of switching to Ferrite, once you're sure of no problems with the module.
As well as the other recommendation of using them on the breadboard. I do think I'll take THAT up, as well! (Now that I'm breadboarding everything first. Nod of respect to Scott for that influence.  ) |
|
|
Back to top
|
|
|
Randaleem
Joined: May 17, 2007
Posts: 456
Location: Northern CA, USA
|
| Posted: Wed Oct 31, 2007 11:55 pm Post subject:
|
|
|
| Rykhaard wrote: | | This pic shows my now standard layout, since converting to 4 pin Molex connectors, a couple of months ago. (The 0.156" spacing ones) |
Hi Ryk!
Mind if I share a couple of thoughts while looking at your new standard PWR input?
It looks like you have used one of the pins which would normally be GND in an MOTM system to be a 15V supply for LEDs?
Since you're going down a "new" path here... I'd suggest using a 5 pin connector for a number of reasons.
First, it allows your modules and layouts to be used with normal MOTM/Frac PWR distros. (I know you might not think that matters if you're doing it all for your own use; but it might be nice to have the option to share a layout or sell a module at some point. And morbidly (it IS halloween!) after you're gone, no one will blow up their MOTM or Frac setup thinking the typical connectors you've used signify a compliant PWR input.
Next, it allows you to have a dirty GND to go with your "dirty" power. The way you have it at present you will want to be VERY careful in laying out your GND returns from the LEDs and other "dirty" sources. Otherwise your added dirty power will do you little good.
Finally, I'd suggest you adopt a 5V supply for your dirty needs, including LEDs. The highest Vdrop for some specialised LEDs is still within its capability and all normal LEDS (including blue and white) will be fine.
But you then also have a ready "digital" supply which will allow for higher amperage at lower cost. Anyone who thinks the next few years are not going to have A)more digital modules and digital portions OF modules, and B)lower voltage parts in general, is IMO not paying attention to what's going on "out there".
So the 5 pins would be +5,+15,DG,G,-15. By using .2sq. of PCB space you gain many benefits.
Still works with MOTM and FRAC modules, is dirty GND capable, doesn't waste power lighting LEDs, and handles any digital options with easy/cheap sourcing of 5V power supplies at high amps. (Which can equal More LED's!)
Just some thoughts thunk while reading and lookin'. YMMV.
Kind regards, Randal |
|
|
Back to top
|
|
|
neandrewthal
Joined: May 11, 2007
Posts: 672
Location: Canada
|
| Posted: Thu Nov 01, 2007 8:11 am Post subject:
|
|
|
| I've noticed my CGS psycho LFO has ferrites between the power and the circuit but do I need to add them to all my mfos modules? I'm thinking I could put them directly in the +/-12 holes and solder my power wires to them. |
|
|
Back to top
|
|
|
frijitz
Joined: May 04, 2007
Posts: 1734
Location: NM USA
Audio files: 54
|
| Posted: Thu Nov 01, 2007 8:18 am Post subject:
|
|
|
| Rykhaard wrote: | | This pic shows my now standard layout... |
Just out of curiosity, why do you have the resistor after the cap rather than before? If you want to block ps noise from your module shouldn't they be the other way around?
Ian |
|
|
Back to top
|
|
|
Rykhaard
Joined: Sep 02, 2007
Posts: 1290
Location: Canada
|
| Posted: Thu Nov 01, 2007 8:28 am Post subject:
|
|
|
| frijitz wrote: | | Rykhaard wrote: | | This pic shows my now standard layout... |
Just out of curiosity, why do you have the resistor after the cap rather than before? If you want to block ps noise from your module shouldn't they be the other way around?
Ian |
Ummmm uhhhhhhh, cuz!  Thanks greatly for clearing my head on THAT one, Ian.
There're so many holes in what I know, electronically - with teaching myself.  Thank you for letting me know about that one.
I hadn't thought of the cap. as a filter itself at all in that place - but only as a current buffer for the module.
(Wondering where my HUGE reply to Randal went ...... Will have to retype it.) |
|
|
Back to top
|
|
|
frijitz
Joined: May 04, 2007
Posts: 1734
Location: NM USA
Audio files: 54
|
| Posted: Thu Nov 01, 2007 1:04 pm Post subject:
|
|
|
| Rykhaard wrote: | | I hadn't thought of the cap. as a filter itself at all in that place - but only as a current buffer for the module. |
Probably doesn't make much difference in practice. If all your modules are as you show, then they are isolated from each other. (i.e., the filters keep noise generated by the modules off the ps lines.) But still seems best practice to have the caps connected to the module ps voltages (i.e. the IC ps pins) rather than the distro bus, since it is the *circuits* that you want to stabilize.
Ian |
|
|
Back to top
|
|
|
Rykhaard
Joined: Sep 02, 2007
Posts: 1290
Location: Canada
|
| Posted: Thu Nov 01, 2007 10:52 pm Post subject:
|
|
|
| frijitz wrote: | | Rykhaard wrote: | | I hadn't thought of the cap. as a filter itself at all in that place - but only as a current buffer for the module. |
Probably doesn't make much difference in practice. If all your modules are as you show, then they are isolated from each other. (i.e., the filters keep noise generated by the modules off the ps lines.) But still seems best practice to have the caps connected to the module ps voltages (i.e. the IC ps pins) rather than the distro bus, since it is the *circuits* that you want to stabilize.
Ian |
I've only been capping the chips directly over my current build period (since July 2005). I hadn't done that in the 90's. The differences that I've enjoyed FROM doing that now, have been immense!
My online electronics mentor / teacher in 1991, taught me about buffering each module, in my earliest days of modular building. I'd been doing 100uF on each module's +V and -V input until last year when I realized those that were doing it, were using 10-22uF, which I've switched to.
Before any buffering though - the headaches that I had with cross module noise, were insane.
Yes - I do buffer every single module input that way. (Also, with my recent addition of the +15V wallwart for my pile of LEDs - I buffer it as well and will be converting all hookups to running the LED's Ground, back to the star distribution point that I use, rather than at the module itself. Thanks to Randal for pointing that one out to me.
So much to learn - and so short a life. |
|
|
Back to top
|
|
|
Tronato
Joined: Sep 21, 2007
Posts: 274
Location: Florida
Audio files: 2
|
| Posted: Tue Dec 04, 2007 7:21 pm Post subject:
|
|
|
Hello!
On 2 of Ken Stone's PCBoards (CGS 32 and CGS 41) he recommends Ferrite Beads or 10 ohm resistors... so what's the deal? 10R or 22R?
Thanks!
TRON |
|
|
Back to top
|
|
|
frijitz
Joined: May 04, 2007
Posts: 1734
Location: NM USA
Audio files: 54
|
| Posted: Tue Dec 04, 2007 8:30 pm Post subject:
|
|
|
| Tronato wrote: | | On 2 of Ken Stone's PCBoards (CGS 32 and CGS 41) he recommends Ferrite Beads or 10 ohm resistors... so what's the deal? 10R or 22R? |
I think 18R sounds creamier. |
|
|
Back to top
|
|
|
bubblechamber
Joined: Nov 04, 2006
Posts: 280
Location: NYC
Audio files: 1
|
|
|
Back to top
|
|
|
toppobrillo
Joined: Dec 10, 2005
Posts: 766
Location: oakland, ca
G2 patch files: 1
|
| Posted: Wed Dec 05, 2007 12:59 am Post subject:
|
|
|
| Quote: | | I think 18R sounds creamier. |
hah! |
|
|
Back to top
|
|
|
Sound
Joined: Jun 06, 2006
Posts: 842
Audio files: 1
|
| Posted: Wed Aug 26, 2009 4:01 pm Post subject:
|
|
|
| Rykhaard wrote: |
So much to learn - and so short a life. |
Yes it is like this. |
|
|
Back to top
|
|
|
Peake
Joined: Jun 29, 2007
Posts: 1113
Location: Loss Angeles
Audio files: 3
|
| Posted: Fri Aug 28, 2009 1:56 pm Post subject:
|
|
|
Vintage Buchla modules also use low 'r' values at high wattage (2? IIRC).
Ferrite beads will not likely free you from whatever evil you may worry about incurring from your modern power supply. Drifting voltages, line noise, spikes, hum, are all part of the past.
Which is why I build and use vintage power supplies, of course...
_________________
We are selling emotions, there are no emotions in a grid. -mwagener
"IC 741. Sometimes you don't want fidelity." -Small Bear Electronics Catalog |
|
|
Back to top
|
|
|
fonik
Joined: Jun 07, 2006
Posts: 3950
Location: Germany
Audio files: 23
|
| Posted: Tue Feb 16, 2010 3:19 am Post subject:
|
|
|
one more question: even ferrite beads have different resistance, i.e. 100R.
how would that influence my circuit?
am i right to assume that if i power the module with 15V and it draws 20mA a 100R bead would cause a drop of 2V?
I x R = V or
0.02A x 100R = 2V
and the energy the ferrite will dissipate would be 2V x 0.02A = 0.04W?
or am i completely wrong about the ferrite's resistance?
_________________
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source |
|
|
Back to top
|
|
|
Sound
Joined: Jun 06, 2006
Posts: 842
Audio files: 1
|
| Posted: Tue Feb 16, 2010 3:28 am Post subject:
|
|
|
Please correct me if I'm wrong, Its just a thought:
-A resistor itself doesn't drop a voltage.
-It's the voltage divider made up by the impedance input and the impedance of the circuit. I mean the resistance of these ferrite beads and the resistance of the circuit to ground. |
|
|
Back to top
|
|
|
fonik
Joined: Jun 07, 2006
Posts: 3950
Location: Germany
Audio files: 23
|
| Posted: Tue Feb 16, 2010 4:26 am Post subject:
|
|
|
| Sound wrote: | Please correct me if I'm wrong, Its just a thought:
-A resistor itself doesn't drop a voltage. |
no, it's the current over resistance. so if my module draws 20mA on the positive rail, a 100R resistance would cause the voltage to drop from 15V to 2V according Ohm's law.
BTW i am more interested in the wattage...
_________________
cheers,
matthias
____________
Big Boss at fonitronik
Tech Buddy at Random*Source |
|
|
Back to top
|
|
|
|
Forum index » DIY Hardware and Software
FAQ
Calendar
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
Chat Room
