chrisq <syseng@gfsys.co.uk>wrote:On 9/7/26 16:18, john larkin wrote:>
Suppose we have a box with some big caps inside, for example 0.2
farads that run at about 200 volts. When AC power is off, we want to
discharge them for several reasons.
Putting, say, a 1K resistor across them dissipates 40 watts and has a
200 second time constant. It will take many tau before the voltage
gets low enough for people to poke around inside.
The ideal discharger would be a constant-current or even better a
constant-power load, all the way down to zero volts. It would be dumb,
not switched by some decision circuit or anything fancy like that.
And of course we need several LEDs as warnings that the thing is hot.
What sort of design needs 0.2 Farad cap, at 200 volts ?. If you are
working at that level, put in a cheap relay and a rated heatsink
wirewound resistor to dump the energy, when the power goes off.
Cheap, and lossless as well. Motor drive inverters often have
big resistors to brake the motor.
No relay, use an thyristor
| Date | Sujet | # | Auteur | |
| 7 Sep 26 |  discharging caps | 162 | john larkin | |
| 7 Sep 26 |  Re: discharging caps | 7 | Simon Simple | |
| 7 Sep 26 |   Re: discharging caps | 6 | john larkin | |
| 7 Sep 26 |   Re: discharging caps | 1 | Simon Simple | |
| 8 Sep 26 | Re: discharging caps | 4 | legg | |
| 8 Sep 26 | Re: discharging caps | 1 | john larkin | |
| 8 Sep 26 | Re: discharging caps | 2 | Phil Hobbs | |
| 8 Sep 26 | Re: discharging caps | 1 | john larkin | |
| 7 Sep 26 | Re: discharging caps | 12 | ehsjr | |
| 7 Sep 26 | Re: discharging caps | 11 | john larkin | |
| 7 Sep 26 | Re: discharging caps | 2 | Liz Tuddenham | |
| 7 Sep 26 | Re: discharging caps | 1 | john larkin | |
| 8 Sep 26 | Re: discharging caps | 8 | Jan Panteltje | |
| 8 Sep 26 | Re: discharging caps | 7 | john larkin | |
| 8 Sep 26 | Re: discharging caps | 6 | Jan Panteltje | |
| 8 Sep 26 | Re: discharging caps | 5 | john larkin | |
| 9 Sep 26 | Re: discharging caps | 4 | Jan Panteltje | |
| 11 Sep11:54 | Re: discharging caps | 3 | Simon Simple | |
| 11 Sep12:01 | Re: discharging caps | 1 | Jan Panteltje | |
| 11 Sep14:59 | Re: discharging caps | 1 | Phil Hobbs | |
| 7 Sep 26 | Re: discharging caps | 2 | Bill Sloman | |
| 7 Sep 26 | Re: discharging caps | 1 | john larkin | |
| 7 Sep 26 | Re: discharging caps | 87 | chrisq | |
| 7 Sep 26 | Re: discharging caps | 84 | john larkin | |
| 8 Sep 26 | Re: discharging caps | 62 | Bill Sloman | |
| 8 Sep 26 | Re: discharging caps | 4 | john larkin | |
| 8 Sep 26 | Re: discharging caps | 3 | Bill Sloman | |
| 8 Sep 26 | Re: discharging caps | 2 | john larkin | |
| 9 Sep 26 | Re: discharging caps | 1 | Bill Sloman | |
| 8 Sep 26 | Re: discharging caps | 57 | john larkin | |
| 8 Sep 26 | Re: discharging caps | 56 | Bill Sloman | |
| 8 Sep 26 | Re: discharging caps | 55 | john larkin | |
| 9 Sep 26 | Re: discharging caps | 54 | Bill Sloman | |
| 9 Sep 26 | Re: discharging caps | 53 | piglet | |
| 9 Sep 26 | Re: discharging caps | 52 | john larkin | |
| 9 Sep 26 | Re: discharging caps | 1 | Bill Sloman | |
| 9 Sep 26 | Re: discharging caps | 50 | Jeroen Belleman | |
| 9 Sep 26 | Re: discharging caps | 9 | Bill Sloman | |
| 9 Sep 26 | Re: discharging caps | 6 | john larkin | |
| 9 Sep 26 | Re: discharging caps | 5 | Bill Sloman | |
| 9 Sep 26 | Re: discharging caps | 4 | john larkin | |
| 10 Sep 26 | Re: discharging caps | 3 | Bill Sloman | |
| 10 Sep 26 | Re: discharging caps | 2 | john larkin | |
| 10 Sep 26 | Re: discharging caps | 1 | Bill Sloman | |
| 9 Sep 26 | Re: discharging caps | 2 | chrisq | |
| 9 Sep 26 | Re: discharging caps | 1 | Bill Sloman | |
| 9 Sep 26 | Re: discharging caps | 40 | Bill Sloman | |
| 9 Sep 26 | Re: discharging caps | 37 | Jeroen Belleman | |
| 10 Sep 26 | Re: discharging caps | 36 | Bill Sloman | |
| 13 Sep01:27 | Re: discharging caps | 35 | Waldek Hebisch | |
| 13 Sep01:38 | Re: discharging caps | 20 | Lane W | |
| 13 Sep04:11 | Re: discharging caps | 19 | Waldek Hebisch | |
| 13 Sep15:50 | Re: discharging caps | 18 | john larkin | |
| 13 Sep16:14 | Re: discharging caps | 3 | Lane W | |
| 13 Sep17:18 | Re: discharging caps | 2 | Bill Sloman | |
| 13 Sep17:28 | Re: discharging caps | 1 | Lane W | |
| 13 Sep16:28 | Re: discharging caps | 14 | Bill Sloman | |
| 13 Sep20:03 | Re: discharging caps | 13 | john larkin | |
| 13 Sep23:54 | Re: discharging caps | 9 | Simon Simple | |
| 14 Sep01:12 | Re: discharging caps | 8 | john larkin | |
| 14 Sep07:05 | Re: discharging caps | 7 | Bill Sloman | |
| 14 Sep16:21 | Re: discharging caps | 6 | john larkin | |
| 15 Sep09:28 | Re: discharging caps | 5 | Bill Sloman | |
| 15 Sep18:23 | Re: discharging caps | 4 | john larkin | |
| 16 Sep09:39 | Re: discharging caps | 3 | Bill Sloman | |
| 16 Sep11:21 | Re: discharging caps | 2 | john larkin | |
| 16 Sep12:16 | Re: discharging caps | 1 | Bill Sloman | |
| 14 Sep06:59 | Re: discharging caps | 3 | Bill Sloman | |
| 14 Sep16:22 | Re: discharging caps | 2 | john larkin | |
| 15 Sep09:31 | Re: discharging caps | 1 | Bill Sloman | |
| 13 Sep01:59 | Re: discharging caps | 3 | john larkin | |
| 13 Sep05:21 | Re: discharging caps | 1 | wmartin | |
| 13 Sep07:27 | Re: discharging caps | 1 | Bill Sloman | |
| 13 Sep07:24 | Re: discharging caps | 11 | Bill Sloman | |
| 13 Sep14:36 | Re: discharging caps | 10 | Waldek Hebisch | |
| 13 Sep17:05 | Re: discharging caps | 9 | Bill Sloman | |
| 13 Sep19:40 | Re: discharging caps | 8 | John R Walliker | |
| 13 Sep20:08 | Re: discharging caps | 4 | john larkin | |
| 14 Sep07:18 | Re: discharging caps | 3 | Bill Sloman | |
| 14 Sep16:24 | Re: discharging caps | 2 | john larkin | |
| 15 Sep09:36 | Re: discharging caps | 1 | Bill Sloman | |
| 14 Sep07:11 | Re: discharging caps | 3 | Bill Sloman | |
| 14 Sep16:56 | Re: discharging caps | 2 | john larkin | |
| 15 Sep09:50 | Re: discharging caps | 1 | Bill Sloman | |
| 10 Sep 26 | Re: discharging caps | 2 | john larkin | |
| 10 Sep 26 | Re: discharging caps | 1 | Bill Sloman | |
| 8 Sep 26 | Re: discharging caps | 14 | chrisq | |
| 8 Sep 26 | Re: discharging caps | 1 | chrisq | |
| 8 Sep 26 | Re: discharging caps | 12 | john larkin | |
| 8 Sep 26 | Re: discharging caps | 3 | chrisq | |
| 8 Sep 26 | Re: discharging caps | 2 | chrisq | |
| 9 Sep 26 | Re: discharging caps | 1 | john larkin | |
| 8 Sep 26 | Re: discharging caps | 5 | Bill Sloman | |
| 8 Sep 26 | Re: discharging caps | 4 | john larkin | |
| 9 Sep 26 | Re: discharging caps | 3 | Bill Sloman | |
| 9 Sep 26 | Re: discharging caps | 2 | john larkin | |
| 9 Sep 26 | Re: discharging caps | 1 | Bill Sloman | |
| 8 Sep 26 | Re: discharging caps | 1 | Bill Sloman | |
| 14 Sep17:44 | Re: discharging caps | 2 | Buzz McCool | |
| 14 Sep18:15 | Re: discharging caps | 1 | john larkin | |
| 11 Sep07:23 | Re: discharging caps | 3 | Bill Sloman | |
| 17 Sep08:19 | Re: discharging caps | 4 | Cydrome Leader | |
| 8 Sep 26 | Re: discharging caps | 2 | Jan Panteltje | |
| 7 Sep 26 | Re: discharging caps | 20 | Lasse Langwadt | |
| 8 Sep 26 | Re: discharging caps | 1 | legg | |
| 9 Sep 26 | Re: discharging caps | 1 | Jeremiah Jones | |
| 9 Sep 26 | Re: discharging caps | 17 | someone | |
| 9 Sep 26 | Re: discharging caps | 6 | Joerg | |
| 13 Sep19:52 | Re: discharging caps | 8 | legg |
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