Hi guys,
after posting some pics of my 1U rack with four effects in the Pictures thread I got questions about the relay switching I used. So, as suggested, it's best to post about it in a separate thread.
(http://img392.imageshack.us/img392/1412/p1040292largejd2.th.jpg) (http://img392.imageshack.us/my.php?image=p1040292largejd2.jpg)(http://img111.imageshack.us/img111/7439/p1040306largefp3.th.jpg) (http://img111.imageshack.us/my.php?image=p1040306largefp3.jpg)
The rack holds four effects (BYOC overdrive, triboost, compressor and envelope filter). The switching is done with DPDT relays (one for each effect) and the relays are controlled by regular DPDT switches in the grey stompbox.
(http://img220.imageshack.us/img220/2910/p1040263largeob8.th.jpg) (http://img220.imageshack.us/my.php?image=p1040263largeob8.jpg)(http://img220.imageshack.us/img220/7187/p1040270largezx3.th.jpg) (http://img220.imageshack.us/my.php?image=p1040270largezx3.jpg)
Here's a schematic of two relays (please note, that the series resistors R1, R3 and so on should be omitted). Basically when a switch is used to connect TO_SWITCH and FROM_SWITCH the relay will change state and the signal is then sent effect board and back from it to the next relay. There's also an option for a LED when this is done. I didn't use these LEDS, but they can be used in the rack front panel as indicators.
(http://img389.imageshack.us/img389/5986/conceptbm3.gif) (http://imageshack.us)
(http://img389.imageshack.us/img389/conceptbm3.gif/1/w753.png) (http://g.imageshack.us/img389/conceptbm3.gif/1/)
Here's a quick idea of what's in the foot controller. Each effect/relay has it's own foot switch that simply connects the two signal mentioned above and lights either a green or red LED (depending on state). I used bicolor LEDs, but that doesn't change basically anything.
(http://img242.imageshack.us/img242/7021/footswitchpz9.gif) (http://imageshack.us)
(http://img242.imageshack.us/img242/footswitchpz9.gif/1/w882.png) (http://g.imageshack.us/img242/footswitchpz9.gif/1/)
Overall the schematics are a bit crappy (as I added a bunch of GND and Vcc pads in the last minute), but the board layouts are fine. The regulator board is nothing special, just two 7812 regulators. One feeds the relay and the other one is used for the effect boards. I didn't want both the relays and the effects behind the same regulator, as I had my concerns about the switching noise it might cause. So far the dual regulators have worked well.
These were the first boards I had etched and to be honest the layout has too thin nets and isolation distances for etching. But I will redraw both boards into a single PCB as I will have them redone into a properly manufactured PCB. I'll try to make it more etchable while I'm at it.
I uploaded the Eagle 5.2.0 project file here => http://www.youshare.com/Guest/0d92b3425747d0fe.zip.html
Any questions, just ask!
BR,
Aleksi
what to say ? THANKS
Good job m8
Armando
Thank you and my pleasure! :icon_smile:
BR,
Aleksi
Hmmmm.. something's wrong :icon_confused:
Was playing around with that thing, worked OK and plugged the transformer out of the wall socket. Went to have few hours of sleep and when I plug power to thing it powers on OK. However when I connected the control voltage to the FET gate the power supply sagged, indicating a short or similar. Couldn't find the cause for the problem by measuring, so I replaced one of the FETs. Bang, that relay was working again. It seems that all four FETs had "burned" so that they were conducting constantly (even with the gate voltage at 0V) and also seemed to draw the gate to near GND (that might explain the sagging, as the control signals don't have a series resistor at the moment).
I don't get it.... The relay has "discharge" diodes, the BS170 FET should handle the current and the gate voltage is within the datasheet range. And how the hell can all four FETs break down at the same time.
Off to do some thinking.
EDIT: The relay diodes are 4148, although 400x would be better. But all the diodes are OK, so I doubt that is the cause. Although the damage would indicate a problem with relay diode.
The BS170 is a MOSFET. It is very sensitive for static voltages. Because of the high impedance of the gate, the FET is easily destroyed by touching the gate for instance via the "from switch" input. Add some protection diodes (or a zener), one from the gate to ground and one from the gate to the power supply. (search SHO booster where the same is done.)
A good alternative is to use a ULN2803 relay driver chip. These are low cost, use darlington transistors and already have snubber diodes for discharging the relays.
Hi Flo,
I honestly didn't even think about that, thank you very much! Will add the zeners to schematics and layouts (along with substituting the 4148s with 400x in the layout)
For the current board it might be easiest / cleanest to look if we have any MOSFETs at work that have the builtin protection zener.
BR,
Aleksi
Aleksi, where did you get the empty 1U enclosure? Was is something you salvaged or a new enclosure that you found somehwere? This looks great, I think I am going to have to do this.
Thanks Ripthorn,
I got it from the german pedal parts supplier Banzai Music (along with other stuff I need - some odd components, LED bezels etc etc)
Here's a link to their rack page http://www.banzaieffects.com/19-Inch-Rack-Enclosures-c-810.html
It actually seems they don't have the 1U rack in black, the price was about 30€ which I considered quite cheap. They're available here in Finland for something like 50-60€.
But I think your best bet is an electronics supplier or eBay.
BR,
Aleksi
update relay schematic and layout (includes the BS170 zener protection diode from GND to Gate, snubber diodes changed to 1N400x and added correct series resistors for the gate signals)
http://www.youshare.com/Guest/7fba70990f147f25.zip.html
BR,
Aleksi
Wow - Aleksi - this is exactly the kind of switching that I have been looking for!!! I'll be the first to admit that I don't have the knowledge to piece together the various relay switching articles that R.G. has been kind enough to post. :icon_redface:
I get the concepts but it wasn't the exact schem/layout I was looking to incorporate into my setup. Modifying it to fit my needs a skill set that I don't have at this point.
Your schem fits what I need and I think it has opened up a few mental doors for me... thank you!!
-chris
Thanks Chris! I'm really happy people have found the effect rack helpful with their own projects.
Aleksi- thanks a lot for this info. i've been wanting to do a rackmounted effects unit for a while but honestly it's a little over my head. you just put me one step closer ;D
+1 on the thanks, Aleksi. :)
Good work - please keep us updated on your progress. This is just at the right level for me - I was (and still am) into R.G.'s stuff, but it was just a little bit of a stretch for my abilities. This solution appears simple and repeatable - I even breadboarded a basic version to test it out the other day and was happy with the result.
One question - in your completed system do you hear any pop/click when switching effects in and out, or is it totally silent? My breadboard version was OK, but it was not mounted in an RF-free enclosure and I was only using a couple of hastily rigged up noisy power supplies. I suppose I'm really asking how does it sound at performance volume? :icon_biggrin:
Thanks again for sharing,
turkey101
Very cool project ! I was wondering where you got your rack chassis from?
"Very cool project ! I was wondering where you got your rack chassis from?"
See reply #7 from Aleksi:
http://www.banzaieffects.com/19-Inch-Rack-Enclosures-c-810.html
turkey101
Turkey, Burningman and Deaconque: Thank you!
Well, I would say that thing makes about the same noise as a normal 3PDT with proper pull down resistors at the effect inputs/outputs and proper power supply filtering (practically none?). I play at home with quite low volumes, but I can't hear any pops.
Although, I think there might be a chance of hearing something if you have the guitar signal cables physically close to the relays... I think the signal wire could pick up some noise from the relay's coil when you change states. But I haven't that problem and my signal cables are about ~2cm on the PCB from the relays.
My next job is to slighly mod the caps on the Tubescreamer (change the lowpass filter higher after the clipping op-amp) and maybe change some freq caps on the envelope filter too. Other than that it's done. So trying to decide what's next. I kind of have my eyes set on those Weber tube amp kits, but will see. Although a 1U rack with all tube based effects would be nice :D
BR,
Aleksi
Now it's done. Update the TS and Envelope Filter caps. I thought the TS808 sounded really muddy with the stock low pass filter after the clipping, really needed the tone pot to be set to fully clockwise. Now with the low pass filter corner frequency higher the tone pot is usable through the entire range. Altered the sound quite a bit too, now it sounds like I expected a Tubescreamer to sound.
Hi Aleksi. I have a few questions about relay switching, and thought that maybe you or someone else could help. I've read the switching and relay articles at GEO, and I've read quite a bit at other sites. I think I just need clarification.
My question is: Why use a transistor to switch the relay on and off instead of just using a switch?
From what I have gathered, the reason is to slow down the activation/deactivation of the relay a bit. This slowdown is necessary to prevent capacitance between the relay coil and the actual switched contacts on the relay, and that doing this helps prevent clicks or pops when the relay is switched. Is this correct?
Last, why use a Mosfet? I've read a few documents like this one (http://www.jaycar.com.au/images_uploaded/relaydrv.pdf) [pdf] that use regular NPN transistors. Is there any benefit in using a Mosfet, or will a regular transistor do the job just as well?
The reason I am asking is because I'm building a multi-effects unit kind of like yours, but with 8-10 effects, and I'm putting it in a Hammond 1456 sloped enclosure. Each effect will have it's own in/out jacks wired up like the Jimi-In-A-Box design so I can repatch the order of the effects. The switches will be towards the front of the enclosure, and the pots and circuit boards will be mounted near the back. That means that for each effect, the signal would come in the jack and go to the switch (11 inches), and return from the switch to the output jack (11 more inches). If the effect is engaged, the signal has to travel to the circuit board (8 inches) and back to the switch (8 more inches). So I'm looking at 38 inches of cabling per effect, and if I have 10 effects I am looking at 32 feet of cabling. I could easily mount the circuit boards right by the switches to shave 16 inches of cabling off each effect, but since my potentiometers are near the back, I would then have to add 16 inches of cabling for each potentiometer-- not a good idea. So the plan is to have dpdt switches up front run the LEDs and the relays that are near the back, between the jacks and the circuit boards. It also comes out cheaper to use relays and DPDT switches than to use 3PDT switches, especially when you consider the cost for all that shielded wire.
Thanks for any input you can provide!
Mike
You can control the relay directly via a 1PDT (or 2PDT) switch, no need for a transistor.
But dont' ommit the snubber diode!
Slightly off topic but what mods did you do to the Tube Screamer? I'm assuming you changed the cap values - just wondering what you changed.
Thanks!
-chris
Quote from: Aleksi on January 05, 2009, 01:54:52 AM
Other than that it's done. So trying to decide what's next. I kind of have my eyes set on those Weber tube amp kits, but will see. Although a 1U rack with all tube based effects would be nice :D
BR,
Aleksi
You may want to check out www.ax84.com
They have a boat load of great amp projects. www.18watt.com also is for people wanting to build a Marshall 18W amp.
You will have to build a head enclosure for your head unit, but going this route you get to pick all the components that go into it. I built my current gigging amp that way and I absolutely love it.
Mike, that's a good question. Honestly I don't know why should use a transistor over a regular switch if just use it for switching the relay. Since I've been to school I've always just seen the "use a transistor to control a relay" everywhere. So R.G. (or someone else with experience with audio electronics) might give you a full explanation about the benefits of one over the other. But I would GUESS using the switch directly might cause pops/noise due to the relay / switch contacts bouncing. If you try it, please let us know how it sounds!
The reason why I used transistors, is that it gives me a bunch of other nice options for the future (as I'm getting these PCBs done properly) and also allowed me to add the option of "in-rack LEDs" by using the MOSFET gate voltage to turn on the LED. In the future it also allows me to use, for example, TTL level signals to control the relay which expands the possibilities if I want to use it with a micro controller.
I opted to use the BS170 MOSFET over a NPN transistor, because I have quite a few BS170s lying around :) But you can use a NPN transistor for switching also, and I think most examples on the internet are ones with a NPN transistor.
Your project indeed would call for some remote switching. My reason for using the relays was the same as yours. Running the signal wires several metres to the footswitch and back would have been a sure way of getting all the possible noise in the signal line.
Chris, the list of mods / options I did to the TS are
- front panel switches for a) gain boost, which adds a 470k resistor in series with gain pot b) bass boost, which allows to switch between the stock 47nF and 330nF cap in the clipping op amp section. This brings in more bass to the to distorted signal.
- front panel clipping rotary switch, allows me to choose the clipping method from a) symmetrical 1N4148 b) asymmetrical 1N4148 c) symmetrical LED and Ge diode d) symmetrical MOSFET e) symmetrical 1N4001 and Ge f) Clean boost, no clipping
- After the first op amp section (clipping) there is a low pass filter made with 1k/220nF. I switched the cap to 100nF which allows more highs in to the circuit. This made tone pot useful through out it's whole range. Now this is probably gear specific, I tuned the circuit for Strat.
Chill, thanks, I actually checked the ax84 project a few days back. But the 18watt website was new, will head there now! I currently have about ten websites open.... Weber, Ceritone, Mojo, Ampmaker etc. The Weber kits would be great for me as they would allow me to make a complete set with nice covers and so on. But the problem is that I really could use a master volume in those kits and that would cost extra money. Also the shipping and taxes increase the price. So right now looking at european alternatives, atleast for places that offer speaker cabines and amp cabinets for a reasonable price. The UK company Ampmaker has two nice kits and with the current cheap pound in respect to the euro I could really go for one of those! Will see.
BR,
-Aleksi
Quote from: Aleksi on January 06, 2009, 01:23:29 AM
Chris, the list of mods / options I did to the TS are
- front panel switches for a) gain boost, which adds a 470k resistor in series with gain pot b) bass boost, which allows to switch between the stock 47nF and 330nF cap in the clipping op amp section. This brings in more bass to the to distorted signal.
- front panel clipping rotary switch, allows me to choose the clipping method from a) symmetrical 1N4148 b) asymmetrical 1N4148 c) symmetrical LED and Ge diode d) symmetrical MOSFET e) symmetrical 1N4001 and Ge f) Clean boost, no clipping
- After the first op amp section (clipping) there is a low pass filter made with 1k/220nF. I switched the cap to 100nF which allows more highs in to the circuit. This made tone pot useful through out it's whole range. Now this is probably gear specific, I tuned the circuit for Strat.
Thanks!!
-chris
Aleksi - another quick question for you... Are you using the 5V relay? I thought that all G5V-2 were volts (hence the name) but when I went to Mouser I discovered that there were higher voltages available... If I see correctly, you are running this setup on 9V but I just wanted to make sure I'm not missing something.
Thanks again
-chris
Hi Chris,
sorry for the delay in reply, for some reason I didn't get a notification from this thread.
Yes there are several different voltages available for the Omron relays, check here http://www.omron.com/ecb/products/pry/111/g5v_2.html
I used the 12V relays and the system is actually running on 12V now (the regulator board has two 7812 regulators). The relay board probably has the "wrong" Vcc in the schematic as I used the +9V(T) to provide a Vcc with a pad in the layout.
Anyway, the voltage doesn't matter. The circuit should work just fine as long as the Vcc matches the relay's voltage rating. So you can use it with a 9V power supply with the 9V relays. The Omron relays should still work with 75% of the rated voltage, but your always better getting as close to the rated voltage as possible.
BR,
Aleksi
Wow Looks Amazing!! Congratulation!!
Oikeasti, se on niin seksikäs ;).
Regards
D.
Thanks :icon_lol:
ahh! I missed the regulators.... thanks for the post.
-chris
Hi Guys,
Firstly i would like to thank Aleksi for providing his layout and schematic to this unit, it is an excellent idea and implementation, good work.
Secondly i have offered to host his files for him, they are available here http://rapidshare.com/files/205266728/Aleksi_layout_schematic.rar (http://rapidshare.com/files/205266728/Aleksi_layout_schematic.rar) on a premium acc so shouldn't get deleted.
Regards,
D_G
I would like to use this for something I'm building but I have two questions. 1) In that layout what happened to all the grounds? To me they appear to floating. 2) I have already built something similar but have been having some trouble with hum. Does this have any problems like this. 3) (ok so I lied haha) Can you use several of the boards tied together to control more loops? Thanks Curt
Hi Curt,
1) not sure what you mean by floating?
- The regulator board and the relay board have ground planes. Both boards are connected to the chassis with metal standoffs which connects the ground to the chassis.
- The relay board gets Vcc and GND from the regulator board
- Each effect gets Vcc and GND from the regulator board
=> all GNDs are tied together
The relay board only switches the in and out signals, not the ground.
2) No, I haven't had problems with humming. I do get some buzz when I connected the MOSFET booster, compressor and Tubescreamer all at high gain levels, but that's another thing. When I was building this I didn't even think about shielded wires etc.
3) yes you can use multiple boards together, as many as you like. Basically my board with four relays is similar to using four separate boards that would each have just one relay.
Hope that helps, if you have any more questions just fire away! :icon_smile:
BR,
-Aleksi
Yeah I'm sorry if I am confusing you. Basically I am looking for something that I can etch. Cant really etch a ground plane. What layout did you use to etch yours? Thanks in advance!
Hi Curt,
Sure you can etch the GND plane. I used that exact layout for my boards (although I didn't etch them myself, because I don't have the equipment). Basically the difference between etching a "normal" board and one with a ground plane is, that instead of etching most of the copper away it stays on the board as a GND plane.
If you're using Eagle, than the GND plane is not normally visible in the layout, just the GND plane edges. You have to press "Ratsnest" to make it visible in the layout.
BR,
Aleksi
OHHHH I see it now!!! I'm not real familiar with Eagle so it all makes sense now! Your power board. Does is only regulate voltages or are you filtering them as well? I really want to make sure that I eliminate this hum problem. Also are those values set up for 18v or could I use a 9v source in its place.
Hi Curt,
The 18V and 9V symbols on the schematic are incorrect, I used those because they had pads available on the layout. I'm using about 15V (from a regular wall transformer) to feed the regulator board. It has two 12V regulators (LM7812). One for the effects and one for the relays. I used separate regulators, because I was worried that if I used just one then switching the relays might cause noise to be carried to the effects too. So the 18V on the layout is actually 15V and the 9V is actually 12V. You don't have to use 12V just as long you pick the relays according to the operating voltage. I used 12V relays with the 12V operating voltage.
You basically have to use filtering capacitors with regulators. So my setup has 15V in => filter caps => regulator => filter caps => 12V.
If you have a good 9V transformer than you can forget the regulator board and just use it to power the effects and the relays. Adding some filtering caps for the relay would be good too.
BR,
Aleksi
Ok so here is my plan:
I would like to rack mount all my pedal and use this to control them. The pedals will have their very own power supply from this controller. I will be using 1/4 jacks to connect them to the board. Can I also use a different 9v source to run this board or will that cause ground loops? My plan is to run 9v into a regulator board like yours for filtering etc. Then use a 5v regulator to drop it to the rated 5v relays. From there it will be just like your board. If I want to run 5v relays do I need to change any values of components on your board? Thanks
Hi Curt,
if you have a 9V source to feed the effects and the 5V regulators it should work just fine.
If you use the 5V and have the LEDs connected to the MOSFET gates, then you should probably drop the 4.7k (LED series resistors) to about 2.2k and also the 1k series resistor going to the switches to about 500ohms.
BR,
Aleksi
Anyone have the updated schematics that were posted? Links dead!
Hi
you mean the 2 at the beginning of the thread ? here they are
(http://img389.imageshack.us/img389/5986/conceptbm3.gif)
(http://img242.imageshack.us/img242/7021/footswitchpz9.gif)
Cheers
Armando