Power-On Time Delay Circuit

[LinuksGuru]

Hi!

Anyone has damn-simple power-on time delay circuit, for 600-800V and 35 - 60 sec wait time?

I could use RC + zenner + photo-triac + thyristor, but unfortunately, it will not work with "normal" components. With U(C) = U(dc in)*(1-EXP(-t/RC)), U(dc in) = 600V, t=35 sec, R = 150k, 200V zenner diode, C needs to be as much 600uF (600uF/300V cap is simply put too big for so simple purpose). R could not be increased much more otherwise photo-triac will not fire up, or current will be too small for zenner diode.

Schematic should be public domain material.

Thanks in advance for any suggestions.

[boywonder]

I have 2 schematics that I've found while doing a search here, this is the first one. I've built this and it works fine. Uses an amperite time delay relay and an additional single pole relay. You could also use a SS time delay relay instead of the amperite. One nice thing about this design is that is takes the amperite out of the circuit after the delay, allowing it to cool off for proper delay on the next power cycle.

These are both delaying the mains voltage to the power transformer (not 600-800V)

[boywonder]

Here is the other schem, which I have not tried:

[Zero Cool]

I found a circuit in glass audio that uses a 555 timer, very very simple and low parts count and it works great!...wish i could find that article again now...

[Fenris]

I usually use an op-amp as a comparator. It uses a fixed voltage and a R-C and trips a transistor/relay when the R-C reaches that fixed voltage. It's powered from the heater supply, is pretty voltage flexible, and uses only a small number of standard parts.

[zigzagflux]

An option:

http://www.diyaudio.com/forums/showt...15#post1560015

[Wavebourn]

In my version power is delayed until tubes start consuming the current, but I don't think it is useful except when you want to avoid turn-on currents causing thumps in speakers.

A positive feedback by current senses an output current, and starts charging time-delay capacitor faster as soon as senses that the load started to draw current. After an output voltage is set to the regulating value the positive feedback stops working leaving the place on stage to the negative feedback by voltage that keeps output voltage stable.

[LinuksGuru]

Thanks a lot, folks! Actually I have power-on time delay circuit in PS I am going to build, but it also uses relay and Schmitt-trigger based on 6N1P (schematic is back from the 60th).

Replacing relay with photo-triac + thyristor would be just great.

This is simple as 2 * 2 = 4, but my background is software, computers, and printing industry, unfortunately, I do not design schematic for myself.

[Wavebourn]

Originally posted by LinuksGuru


This is simple as 2 * 2 = 4, but my background is software, computers, and printing industry, unfortunately, I do not design schematic for myself.

Hi Andrei,

let me know what you need and I will help you to design. Ask Kubeek, Hearinspace, and others who I helped to, it is an interesting journey!

[atarashi]

Hi,

well, I use the following, it's cheap and works like a charm...

L1 is a relay, the rest should be self explanatory?