| The Shop > Electronics & IC Programing |
| Digital oscilloscope project/kit |
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| Bluechip:
You've no business wiring up 79xx regulators arseaboutface, that's my favourite faff-up. :D BTW, you should really put a 100nF to ground close to the o/p pins on 78xx and 79xx ( and any other regulator for that matter ) otherwise they will tend to oscillate .. :thumbup: Happy New Year 2U and Mrs. Rob ... :wave: Dave |
| RobWilson:
:lol: :lol: Hi Dave I bet it will not be the last time I get a component arse about face :Doh: I will amend the circuit tomorrow as you suggest :thumbup: , I was wondering why I had a strange ripple on the 9 volts out . All the best to you Dave :beer: :ddb: :beer: Cheers Rob |
| Bluechip:
Hi Rob Cheers :beer: First time I had that nonsense was years ago, making a 1MHz Colpitts Oscillator. The circuit was driven by a 7809 and it ekkled quite handsomely at 1.6MHz. No way could I get the damn thing to work properly. Eventually discovered it was the pox-etten 9V with a hideous 1.6MHz ripple .. :doh: Back in my analogue days ... long ago ... Dave |
| RobWilson:
Something like this Dave :wave: I think I will change the output connector to -12, 0 , +5 ,+9, +12 cheers Rob :beer: |
| Bluechip:
Well, 100uF would maybe improve things, but ..... it's the high frequency instability which causes the grief. So, if you actually freakin' READ like what I have writted 100 nF ie. 0.1 uF ... :D :D Electrolytics in general are not very good at getting shot of HF noise 'cos of their inherent construction. An el-cheapo ceramic is all you need. You can leave the 100uF caps. there. Won't harm anything. Good day to you, Sir ... :ddb: Late lunch today ... starving .... BTW I think your 0V centre-tap should be grounded ?? And that is the symbol for a safety earth, ground is an inverted triangle. :thumbup: What current are you drawing from these regulators anyway? The 12V ic's. will have some 25V i/p, this gives about 13V dropped across them. If I assume the max. of 1A they will dissipate some 13W which is a lot for a TO220 package without a fairly large heat-sink and/or a fan. A 15 - 0 - 15 transformer would be a bit better ... Dave |
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