# mains first on last off

Discussion in 'General Electronics Chat' started by peten, Jan 22, 2011.

1. ### peten Thread Starter New Member

Jan 22, 2011
6
0
Hi .

I need to control the way certain things are powered up and down again this a crossover and Amps what i need is the crossover to power up first then the amps about 1.5 seconds later but then when it comes to powering down the amps need to go off first the the crossover again about 1.5 seconds later to stop problems of power down squeal

I have no problem with construction being into Ham Radio Computers and general electronics but seem to be having a brain fart right now

Thanks pete .

2. ### tom66 Senior Member

May 9, 2009
2,613
215
Why do you need to do this? Frequently we see the XY problem: you want to solve problem X, but you have come up with solution Y, and you need to know how to solve Y, when you'd be better off solving X. So why do you need to sequence the power? More detail on "power down squeal" would be appreciated.

3. ### peten Thread Starter New Member

Jan 22, 2011
6
0
Hi the reason we need to sequence the power is that the amps and the crossover are built into a box and hidden out the way for one but the main reason is that if we just turn the power off the crossover goes into a loud squeal as the power fades which makes a <snip> of a noise as the amps still have enough power in the filter caps to run for a second or so and it is a <snip> of a noise but it also squeals on power up which is the reason for the first on last off needs

hope this explains it a little for you ..

Pete .

Last edited by a moderator: Jan 22, 2011
4. ### tom66 Senior Member

May 9, 2009
2,613
215
Hmm: 1.5 seconds is a long time, but it might be doable. I'm thinking of keeping a DC relay energised for the required time. What do you think the absolute minimum time would be? And do you have a DC power supply, say somewhere from 6V to 15V?

5. ### peten Thread Starter New Member

Jan 22, 2011
6
0
Hi

12 volts DC not a problem at all

6. ### tom66 Senior Member

May 9, 2009
2,613
215
Not entirely sure this is what you need but it should give you an idea.

Paste this into the circuit simulator on falstad.com/circuit (under the Import menu):

Code ( (Unknown Language)):
1. \$ 1 5.0E-6 15.472767971186109 43 5.0 50
2. v 384 48 384 128 0 1 50.0 325.0 0.0 0.0 0.5
3. 178 512 112 576 112 0 2 0.2 0.06211199747035969 0.05 1.0E9 0.02 20.0
4. w 512 112 496 112 0
5. w 496 112 496 128 0
6. w 496 128 384 128 0
7. w 496 48 496 64 0
8. w 496 64 512 64 0
9. w 496 208 512 208 0
10. w 512 256 496 256 0
11. 178 512 256 576 256 0 2 0.2 0.10672510501676484 0.05 1.0E9 0.02 20.0
12. w 576 272 624 272 0
13. w 576 224 624 224 0
14. r 624 224 624 272 0 100.0
15. x 663 258 742 264 0 24 X-over
16. w 576 128 624 128 0
17. w 576 80 624 80 0
18. r 624 80 624 128 0 100.0
19. x 663 114 718 120 0 24 Amp
20. w 496 256 384 256 0
21. w 384 256 384 128 0
22. w 496 208 448 208 0
23. w 384 48 432 48 0
24. w 432 48 432 208 0
25. w 432 208 448 208 0
26. w 432 48 496 48 0
27. R 336 288 304 288 0 0 40.0 12.0 0.0 0.0 0.5
28. t 448 448 480 448 0 1 -9.172846457729111 0.6926514419357801 100.0
29. t 576 448 608 448 0 1 -10.024620552629905 0.679118510682238 100.0
30. s 336 304 336 368 0 0 false
31. x 246 347 318 353 0 24 On/off
32. w 336 288 336 304 0
33. r 336 416 400 416 0 10000.0
34. c 400 416 400 496 0 4.7E-4 0.6926514419357801
35. g 400 496 400 512 0
36. g 528 496 528 512 0
37. c 528 416 528 496 0 0.0047 0.679118510682238
38. w 336 288 464 288 0
39. w 464 288 512 288 0
40. w 464 288 464 144 0
41. w 464 144 512 144 0
42. r 528 368 336 368 0 10000.0
43. w 400 416 448 416 0
44. w 448 416 448 448 0
45. w 528 368 528 416 0
46. w 576 448 576 368 0
47. w 576 368 528 368 0
48. w 480 432 480 304 0
49. w 480 304 512 304 0
50. w 512 160 496 160 0
51. w 496 160 496 336 0
52. w 496 336 608 336 0
53. w 608 336 608 432 0
54. w 480 464 480 480 0
55. g 480 480 480 512 0
56. g 608 464 608 512 0
57. d 336 368 336 416 1 0.805904783
It's not precise by any means.

File size:
14.5 KB
Views:
20
7. ### studiot AAC Fanatic!

Nov 9, 2007
5,005
519
I remember some years back an aircraft manufacturer had a problem like this.

The result was an interesting exercise in management. The simplified version appears below.

It was necessary to switch on/of pumps in sequence to avoid certain problems. Call the pumps A and B.

Initially a sophisticated logic board was developed with individual switches for pumps A & B and logic interlocks, by the electronics section of R&D.

An alternative relay version was also developed.

The boards were tested by simply trying to switch on A and B simultaneously.

Needless to say cussed humans could beat the circuitry and weck the system.

The final solution ?

An old fashioned multiway mechanical switch labelled 'Switch on A' ; 'Switch on B' was developed.

You could implement the same solution and manually apply the 1 second delays.

go well

8. ### peten Thread Starter New Member

Jan 22, 2011
6
0

Hi Well it seems almost right i will wang a few bit in a breadboard over the next couple of days and see what comes

Thanks so far

Pete .