| ??? 04/06/05 06:42 Read: times |
#91085 - Check your external ground Responding to: ???'s previous message |
Jon:
I found a barbeque piezo extremely usefull for generating fast discharges. I measure about 10ns rise time on my unit. This is much faster than car induction coils (100ns). Recently I had an 89C51RX2 system where I had to have an external BNC connector. The shield of the BNC was directly connected to the CPU ground. The CPU's ground was then connected to the main supply ground "star point" Every time I hit the BNC shield with a barbeque piezo the CPU would go nuts. When I connected the BNC shield directly to the power supply ground "star point" and bypassed the shield to mains ground with a good quality 0.1uF capacitor, the problem disappeared. I think it was caused by hundreds of amps of discharge current into the CPU ground causing the ground to "bounce". I suggest you check your external digital ground. To check it out try isolating it with a 10 ohm resistor or a 50uH inductor in series with your "external" ground. Peter |
| Topic | Author | Date |
| What do you think could happen if... | 01/01/70 00:00 | |
| The 10k from RST to GND | 01/01/70 00:00 | |
| Random resets.. | 01/01/70 00:00 | |
| Dogma. | 01/01/70 00:00 | |
| Oh yea ? | 01/01/70 00:00 | |
| Hmm | 01/01/70 00:00 | |
| brown outs | 01/01/70 00:00 | |
| Obscure | 01/01/70 00:00 | |
| RC Reset circuits. | 01/01/70 00:00 | |
| Something more to it ... | 01/01/70 00:00 | |
| ad wars between Maxim and Microchip | 01/01/70 00:00 | |
| Cutting teeth... | 01/01/70 00:00 | |
| recommend brown out detectors | 01/01/70 00:00 | |
| Which depends on for what.. | 01/01/70 00:00 | |
| built-in reset | 01/01/70 00:00 | |
| Re: Built in brown out? | 01/01/70 00:00 | |
| Better than I did.... | 01/01/70 00:00 | |
| Thanks, Michael. | 01/01/70 00:00 | |
| Why | 01/01/70 00:00 | |
| Other stuff ? | 01/01/70 00:00 | |
| many reasons | 01/01/70 00:00 | |
| Thats not correct. | 01/01/70 00:00 | |
| speak with forked tongue | 01/01/70 00:00 | |
| I agree | 01/01/70 00:00 | |
| re: dogma | 01/01/70 00:00 | |
| ESD events and EMI | 01/01/70 00:00 | |
| Re: Random resets. | 01/01/70 00:00 | |
| Lets not reject the obvious! | 01/01/70 00:00 | |
| no R | 01/01/70 00:00 | |
| RC-circuits are bullshit!! | 01/01/70 00:00 | |
| RC-circuits are bullshit!! | 01/01/70 00:00 | |
| Reset Capacitor | 01/01/70 00:00 | |
| You missed the question! | 01/01/70 00:00 | |
| Why guessing? | 01/01/70 00:00 | |
| RE:Why Guessing | 01/01/70 00:00 | |
| Timing | 01/01/70 00:00 | |
| Update | 01/01/70 00:00 | |
| not necessarily the reset | 01/01/70 00:00 | |
| Other derivatives | 01/01/70 00:00 | |
| if no cap | 01/01/70 00:00 | |
| No Cap | 01/01/70 00:00 | |
| not just a cap, but the right cap | 01/01/70 00:00 | |
| Which cap? | 01/01/70 00:00 | |
| depends | 01/01/70 00:00 | |
| Yes Cap | 01/01/70 00:00 | |
| directly | 01/01/70 00:00 | |
| RE:Directly | 01/01/70 00:00 | |
| yes | 01/01/70 00:00 | |
| Absolutely ! | 01/01/70 00:00 | |
| Update - ESD Problem? | 01/01/70 00:00 | |
| some ways | 01/01/70 00:00 | |
| some ways - more detail please | 01/01/70 00:00 | |
| details | 01/01/70 00:00 | |
| Car induction coil | 01/01/70 00:00 | |
| ESD Problem | 01/01/70 00:00 | |
| Physical Separation | 01/01/70 00:00 | |
| Few Ideas | 01/01/70 00:00 | |
| Re: Few Ideas | 01/01/70 00:00 | |
| Check your external ground | 01/01/70 00:00 | |
| Ya. | 01/01/70 00:00 | |
| now that you are willing | 01/01/70 00:00 | |
| RE:Now that you are willing | 01/01/70 00:00 | |
| alot easier when you know what your look | 01/01/70 00:00 | |
| Not as bad as initially thought. | 01/01/70 00:00 | |
| ground loop | 01/01/70 00:00 | |
| RE: Ground Loop | 01/01/70 00:00 | |
| sound | 01/01/70 00:00 | |
| RE: Ground Loop | 01/01/70 00:00 | |
| It is a loop AND | 01/01/70 00:00 | |
| It's a loop and a flop | 01/01/70 00:00 | |
| no shield can help you there | 01/01/70 00:00 | |
| Kind of machine | 01/01/70 00:00 | |
| so your testbench setup should be OK | 01/01/70 00:00 | |
| Failures | 01/01/70 00:00 | |
| in that case | 01/01/70 00:00 | |
| Materials | 01/01/70 00:00 | |
| could still be ground | 01/01/70 00:00 | |
| Noise resistance | 01/01/70 00:00 | |
| you will not find that | 01/01/70 00:00 | |
| What can be found? | 01/01/70 00:00 | |
| tough these days | 01/01/70 00:00 | |
| Glue ? | 01/01/70 00:00 | |
| No Glue | 01/01/70 00:00 | |
| lesse some pictures. | 01/01/70 00:00 | |
| LOL | 01/01/70 00:00 | |
| Nope | 01/01/70 00:00 | |
| Let the fun begin! | 01/01/70 00:00 | |
| Confession | 01/01/70 00:00 | |
| Confession | 01/01/70 00:00 | |
| Ah. | 01/01/70 00:00 | |
| Not that bad | 01/01/70 00:00 | |
| HAr to see but | 01/01/70 00:00 | |
| Wiring & Filter | 01/01/70 00:00 | |
| Maybe a little better pictures here | 01/01/70 00:00 | |
| nice | 01/01/70 00:00 | |
| Oops - try again | 01/01/70 00:00 | |
| Uh Oh | 01/01/70 00:00 | |
| Yep | 01/01/70 00:00 | |
| Don't ground both ends of shield | 01/01/70 00:00 | |
| bonding | 01/01/70 00:00 | |
| RE: Bonding | 01/01/70 00:00 | |
| Useless.... | 01/01/70 00:00 | |
| Better Pix yet? | 01/01/70 00:00 | |
| Re: Better Pics Yet? | 01/01/70 00:00 | |
| DETAILS... | 01/01/70 00:00 | |
| Nothing hiding here! | 01/01/70 00:00 | |
| !!!!! | 01/01/70 00:00 | |
| I don't think so. | 01/01/70 00:00 | |
| !! | 01/01/70 00:00 | |
| Grounding. | 01/01/70 00:00 | |
| Grounding | 01/01/70 00:00 | |
| Prahlads points | 01/01/70 00:00 | |
| Clarification | 01/01/70 00:00 | |
| Clarification | 01/01/70 00:00 | |
| Update | 01/01/70 00:00 | |
| au contraire | 01/01/70 00:00 | |
| The answer may be on the horizon | 01/01/70 00:00 | |
| not the voltage, but the change | 01/01/70 00:00 | |
| Have a look see | 01/01/70 00:00 | |
| I do not know how good | 01/01/70 00:00 | |
| 7805 Starving | 01/01/70 00:00 | |
| it will go HOT | 01/01/70 00:00 | |
| Heatsink | 01/01/70 00:00 | |
or it's possible | 01/01/70 00:00 |