Okay, I haven’t done the TV yet. I’m waiting on getting some more bulldog leads so I can isolate the switching to just have the TV on but also remove the radio and tape cassette. Originally I wanted them all on at once but wiring it up so they are all on is beyond me so I’m just going to use the Cathode Ray tube and put it in another framework… somewht like the screens in the movie Brazil.
So I’ve finally gotten around to a few things not the least of which was hooking up the boss pedals and spending a bit of time with them. I’ve got a DD-7 digi delay and the RC-2 looper and the possibilities are nearly endless but it’ll be a while before I get my head around them. You know, read the manual as much as you can, even though none of it makes much sense, then go play with the thing for a while then back to the manual where it starts to make more sense… and on it goes.
As for setting up the recording… it doesn’t work on one channel so I’ll have to go through the mixer and figure out where but I’ve an idea and it should be simple enough to fix. Other than that I’ve got to do a switch block on the outs from the PC so I can switch in a simple amp when using the PC for browsing and stuff because otherwise it’s a hassle to switch mixers and amps and the whole caboodle on and off each time… and who needs a valve amp for U-tube clips?
So what I have for you today is the toy thing. In-organic is on again and I picked up a few more battery powered audio toys. Last year I tried sequencing them up but was having problems making them switch as the little toys work on pulsed DC and if you use a transistor to switch them the base voltage interferes with the pulsing DC accross the collector and emitter. I eventually realised, or was told, that the mosfets in a 4066 would do the trick where the control voltage, on the gate, is not interfering with the connection between drain and source. Last year I’d built the sequencer but it didn’t work with the toys so I used it on a drum machine… that kinda works but even that needs work. In the interim I learnt more about 555’s, more than one ever wants to, but now I pretty much have them sussed so I’m having another go at the toy thing.
Shit, I can’t copy and paste the pictures for some reason, they copy but won’t paste into this page… bugger. I’ll restart later and come back to this.
I can do normal copy and paste from here into the address bar so it must be the photbucket site. I couldn’t get the old uploader going until I un-installed flash so maybe something else in there site is fucking me up.
There you go… it works if I open the picture file on its own page then copy the link. Bloody internet. It’s becoming like you bloody need to be a techie.
Anyways above is the schematic. Top left is the power supplies for the toys which run on 3V and 4.5V DC and you can’t get regulators for that voltage easily so I’ve used a dual opamp to divide off the voltages and buffer them out at a low impedance. It’s what we do with a spare opamp section to create the bias for them working as signal amps but it works just as well for a regulated voltage. They should also have a cap, 22-200uf, sitting on the voltage divider from the divided voltage to ground.
Below that is the 555 which is kinda normal except for the 1N914 diode across pins 6 and 7. This shortens the on time and makes it constant so the off times are what changes. The toys just need a quick jolt to get them firing so maybe the 10k from he power rail could be lessened to about 1k or so which’ll quicken it right up. So the diode allows the cap to ground, off pins 6 and 2, to charge up as fast as it can with an almost direct voltage but then it discharges normally through the pot and this sets the off time. Actually there is an amount of time that caps take to charge that is dependant on the size of it so maybe I’m better going to a 4.7uf and a 10 uf and raising the pot to 500k.
So the thng fires off through pin 3 and that goes to the clock of the 4022 which basically cycles that pulse through 8 outputs. The outputs goes to the control inputs of the 4066’s and each time a pulse reaches a control the contacts go from a super high resistance, 100’s of megs, down to almost nothing, a few hundred ohms, so effectively become a switch closed.
To the far right and bottom is a diagram of the mixer to take all the signals from the toys and mix them all to one out. The thing is that these little toys actually use a bridged output which means the signal is divided between two amps, one does the positive swings and the other does the negative swings, from the bias point, and these are combined in the speaker from the 2 outs. What this means is there isn’t a positive out and a ground so I thought about it and realised I could put a voltage divider between the two amp outs and then take the signal from the middle, chuck it through a cap to take out that pesky bias voltage then into regular summing resistors. I tried it and it works. If I discover that one of the toys isn’t bridged I’ll simply go through 1 10k for the hot.
Heres as far as I’ve got. Two etched PCB’s that suffered somewhat in the etching process but theres enough copper to do the job. Saturday today and Monday night is when I want it to be playable.
The only other thing I’ll be doing is having the switch outs on the 4066’s wired up to RCA plugs then have the toys on 2 x 4 banks of RCA sockets. This way I’ll have a cheap patchboard to change the sequencer order or cut what I don’t want. It’s going to be absolutely nuts through fx… this cheap and nasty little sample player.