Digital oscilloscope project/kit

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John Swift:
Hi Rob

I see you have been busy

the kits you have built should come in handy

looking at the power supply
I would fit two 2200uF capacitors

one for the positive supplies and a second for the negative supply

John

PS
I see Bluechip is quicker !!!

RobWilson:
Cheers Dave and John S

Two much improved designs , I like the modifications you made John .

Dave , yours has resistors and diodes added , in simple English why? (anyone)

This power supply is just to run the projects I have built from Banggood , this is their recommendations for the PSU for the signal generator .

I just added bodged on the 9v.

I know it is poor and a much better one could be built , I could just use the three bench PSU I have . I just thought why not have ago at building it and learn a few things on the way , which I have done thanks to you lads :thumbup: and reading up on each component , f&%k lot to take in :palm: , also I am using it as a project to learn how to use the Circuit Wizard software ,its is also something to piss about with in the warm :lol:

The thing is the passed few weeks messing with these boards has got my interest up in learning electronics :med: ,tis all up hill from here :palm:

Dave , what electronics program are you using ?

Thanks again for your input Lads :bow: , keep it coming :poke:

All the best Rob :beer:

Bluechip:
Resistors are to discharge the 2200uF caps. Just considered good practice.

Diodes there to protect regulators from inadvertent connection of reverse voltage from external circuitry. [ If you use PSU for experimenting, anything can happen :zap: Done it. Also, I did use the PSU to drive a small 24VDC motor, all sorts of spikey crap comes off them ].

You should really put more diodes across the regulators to prevent damage by putting volts on the o/p with no power to i/p. Regulators don't like it up 'em the wrong way ... :thumbup: I will amend schematic to show this. Also I notice some wrong component numbering ...

Program is Express PCB. Comes in 2 parts. Schematic and PCB layout. Been mentioned before in this thread, does not export full Gerber file but I etch PCBs myself so it's OK for me. Used to do Eagle but it has a size limit Express PCB does not.

http://www.expresspcb.com/

Dave

Bluechip:
Amended schematic:

This sort of thing is quite common. They all do the same job. Take the 9V regulator.

[1] The 1N4004 across the output. If I shove a reverse voltage into the output, the diode will conduct and effectively prevent any reverse voltage greater than some 0.6V appearing across the o/p to 0V. The regulator lives on.

[2] The 1N4004 connected across the regulator, output to input. If I shove a normal polarity voltage into the output with no volts on the input, the diode will conduct and charge the input capacitor. The reverse voltage across the regulator is again limited to some 0.6V and again the regulator survives.

Regulators don't like outputs higher volts than inputs or outputs lower volts than ground. They often exhibit their displeasure by snuffing it. Bugger eh ??

If you consider it's not going to happen D1 - D8 can be left off, no problem, it'll work just fine without. :clap:

Dave

RobWilson:
Cheers Dave ,

Getting There with this software .

It must be beer O'clock :beer:

Rob

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