Mr modnaR

that looks fine space wise i guess (though, no measurements are shown) - when shall we expect to see Van MidiBoxen on our screens? ;D

sort of, but that method still requires etching, as the toner is the etch resist. what i propose is direct copper 'printing' which would mean no more etching.

ok, i'm going to use a transformer with two 115VAC inputs, and two 6VAC outputs. as i have 240VAC here in the UK, i assume i need to commect the two 'inner' input pins and connect the 250V across the two outer pins, correct? then, to get both 6VAC and 12VAC from the trafo, i need to short the 'inner' pins of the output pins and use the two outer pins for 12VAC and use the shorted connection and one of the outer pins for 6VAC. is that correct? also to rectify the AC, would i then need two rectifiers, or would one do, as in the PSU designs of NorthernLightX and Altitude? many thanks for any help given.

it's not that hard. stretch suitable material across a frame. fill in the 'white' spaces (areas you don't want coloured) with some kind of non water soluble glue. wait for that to dry, and then lightly stipple screen printing ink through the cloth in the areas you haven't blocked with the glue, and voila.

the db9 suggestion wasn't to suppress noise, it was to negate having to put the core etc in the guitar. like i said though, i don't know how much room he's got to play with.

looks good, let us know how you go with that one. i'm thinking now along the lines of getting a 2x6V trafo and using one 6VAC to make the 5V, then using the whole thing together to make the 12V. i only have cores and sids to worry about, so i don't need the -12V.

^^^ that's true, which is why an encoder would be better.

perhaps a 'mod-matrix' style setup would work here, with 707 LEDs and a column of buttons down one side, and a row of buttons along the bottom or top. my 2p

ahh, ok, just read your post Altitude, yeah that's a good design, but how do you work out the values required?

this is how a potential divider works: V2 = (R2 / (R1 + R2)) * V1 basically i think there needs to be two resistors to 'split' the voltage to give 5V (or probably 7V for the 7805). the only trouble with that is that the resistors would need to be able to disspate a fair amount of heat, and would need to be ones with high power ratings (=£$£$£$... :'(). i may be wrong though, i haven't been through in detail what resistances would be needed. i think Alex had the right idea, but forgot the extra resistor.

it's not big: 64mmx82mm, my suggestion was just an alternative so that you wouldn't have to trail power and midi up to the guitar.

My design anticipates a draw of 1A on each rail. I've had the schamatic checked by several guys who DO know their electronics stuff (and I do not), and they approved of the design. You made your own schematic, are you sure you placed everything right? I completed my PSU tonight, but I don't know when I'll be able to test it. As soon as I know anything I'll post it.

going back to the original topic, i believe there could be a far, far better way of producing circuit boards than printing out the resist etc etc. i don't know how many of you know how laser printers work, but basically they have a positively charged roller which is then discharged by a laser in the areas that you want black or whatever colour. then positively charged toner is sprinkled on the roller. this stays on the neutral areas, and doesn't stay on the positive areas. the toner is then transferred to the paper where it is heated. this melts it and fixes it to the paper. how does this translate to circuits? basically a laser printer needs to be set up (or constructed is probably more accurate!) to 'print' a neutral image onto a flat plastic board. the board is then sprinkled with charged fine copper dust, which is then heated to melt it onto the board. et voila! circuits-a-go-go! edit: of course this won't work as i have described it. the copper dust would have to be coated to prevent current flow. another possibility would be that negatively charged areas could be used to attract copper ions in a copper plating setup ??? any thoughts?

i tell you what: Toshio Iwai will be jealous.

wouldn't it be easier to have the core separate from the guitar, and run the leads to the pots and buttons from that to the guitar using a 9 pin RS-232 cable? i don't know how roomy your guitar is, but surely it would be better that way. (it'd also prevent you from having to replace the core every time you smash your guitar up on stage - if you do that sort of thing... ;D)

sounds interesting, aren't mosfets expensive? i only worry because of my clumsiness, and the likelyhood of draining my wallet dry replacing them.... ::);D

ok, i think i've realised the problem. the resistor should have been used as a potential divider. that way the voltage across the 7805 would be dropped and should remain cool. does anyone think it could cause problems when the current draw on the regulator is high though?

hmmm, so what's the solution? cascading voltage regulators? can't think properly at the moment, as i've just fried the fuse in a brand new 12VAC wall wart i got for this psu! i was testing this design on strip board, and had it layed copper tracks down on my work desk. little did i know that there was a renegade leg cut from a capacitor lurking around, and of course did not get noticed until i tried my 9VAC wall wart for my x0xb0x on it first! damn. darwin award here i come.....

i was told in another thread (about the pot that alters lcd backlight brightness), that the resistor acts as a current limiter, and does not drop the voltage significantly. i don't know who to believe. ;D

in addition.

right i've just built this circuit too, with some minor changes, trying to incorporate some of the 'optimised psu'. basically sending 15VDC to the SID module (which still has it's 7812 in place) with a 7815, and then using the 8R2 resistor to try and drop the voltage for the 7805. however, i've found that the resistor idea doesn't seem to knock the voltage down too much, only about 1V, so the 7805 is recieving 16.5V! (the output of the rectifier being 17.5V) and as a result it gets pretty hot. i read on here somewhere that chaining VRs is not a good idea from a noise point of view, but i was thinking of running the 16.5V through a 7812 or 7809 before the 7805 to try and spread the load a bit. it's this a good idea, or not? ps, i have a 12VAC input, but i'm thinking 9V would also work.

you have to remember that the ground on the sid module goes all around the chip. the connection J2 on the sid module has +5VDC and a GND pin. it is there that the chip gets it's ground. hope this helps. ps i had trouble understanding this too at first, but i'm getting there thanks to the kind souls on this forum. 8)

RS do a 330nF in ceramic, but they're £1.06 each and you have to buy ten of them! :o anyone in the UK know of a better place?

ok thanks. i've a much better understanding now thank you.

is it possible to put a load on the psu before attaching it to the midibox core etc to find out the voltages, or would you need to know the current draw of your setup?