Whether you’re speaking about a residence cinema or a computer system, it’s very frequently the case that the more than a few elements of the machine have to be fliped on or off in a relatively explicit order, or at least, routinely. Constructing this sort of automation system is neatly inside the functionality of any electronics enthusiast invaluable of the identify, however on this ‘all-digital’ age, many of the circuits of this kind to be found in newbie electronics magazines or web-sites use a microcontroller. Even although that is indeed a logical solution (in extra meanss than one!), and you would probably even say the easiest one, it does pose issues for all those people who don’t (yet) have the amenities for programming these kinds of IC. So we decided to offer you now an method that’s very different, because it only makes use of a simple, low cost, commonly-avail-able analogue integrated circuit, which in fact doesn’t have to be programmed. Our project in reality makes use of as it’s ‘brain’ an LM3914, a familiar IC from National Semiconductors, usually used for using LED VU (volume unit) meters.
Circuit diagram :
Power-up/down Sequencer Circuit Diagram
Before taking a look on the circuit for our mission, let ’s just remind ourselves that the IC has one analogue enter and ten out-puts supposed for riding LEDs. It can function in ‘point’ mode, where the LEDs light up in flip, from first to last, depending on the enter voltage, but just one LED is lit at any supplyn time. Alternatively it will most probably function in ‘bar’ mode (this is the mode usually used for VU meters), and on this case, the LEDs light up one after the other, in any such means as to create a strip of light (bar) that is longer or shorter according to the enter voltage. This is the mode selected for the LM3914 in the circuit described in some detail under.
So as in an effort to control the AC energyed equipment our sequencer is meant to manage, we're using solid-state relays — four, in our example, although which you can reduce or elevate this number, as so much as a most of ten. Since the enter instruments in solid-state relays are LEDs, they can be driven right away with the help of the LM3914 outputs, for the reason that that’s precisely what they’re designed for. As best 4 relays are on hand, these are unfold across out-puts L2, L4, L6, and L8, however you can choose any arrangement you prefer to go nicely with the quantity of relays you want to have to make use of.
Resistor R7 connected to pin 7 of the LM3914 units the current fed to the LEDs by means of the LM3914 outputs. Here, it’s been set to 20 mA, due to the fact that's the price anticipated by the solid-state relays chosen. The input voltage utilized to pin 5 of the LM3914 is none instead of the voltage present throughout capacitor C1 — and that is the place the circuit is ingenious. When the change is set to ‘on’, C1 charges slowly thru R5, and the LEDs of the solid-state relays on the outputs gentle one after another as this voltage raises; in this approach, the gadgets being keep watch overled are energyed up within the order you’ve chosen. To energy-down, all you have to do is flip the change so that C1 discharges through R5, and the LEDs go out in the reverse order to that wherein they had been lit, in turn energying down the devices connected to the solid-state relays. Easy, isn’t it? If you’re not pleased with the sequence velocity, all you need do is increase or reduce the value of R5 to be in a place to alter the pace one manner or the different.
The circuit needs to be energyed from a volt-age of around 9 to 12 V, which doesn’t even wish to be stabilized. A easy ‘plug-top’, ‘wall wart’ or ‘battery eliminator’ unit will be good, just so long as it is able to supply-ing enough current to power all the LEDs. As the LED present is set by R7 to 20 mA per LED, it’ll be simple for you to work out the current required, according to the collection of solid-state relays you’re the use of.
In our prototype the kind S216S02 relays from Sharp have been used, primarily as a consequence of they proved comfortably on hand via mail order. They even have the good thing about being compact, and their switching capacity of sixteen A means which you can dispense with a heatsink if you’re the use of them for a computer or residence cinema system, the place the present drawn via the vari-ous gadgets will more than likely be expected to stay under 1 A. These solid-state relays should be safe by a fuse, the score of which wants to be chosen according to the current drawn through the tools being powered.
Also no longere the presence across the relay time periodinals of a VDR, sometimes called a GeMOV or SiOV, intended to protect them from any spurious voltage spikes. You can use any sort that ’s intended for operation on 250 VAC with none problem. The prices of fuses F1 to F4 are after all going to rely upon the load being secure.
Construction of the circuit shouldn’t present any particular problem, however as the solid-state relays are connected right away to AC power, it's very important to install it in a fully-insulated case; the case can additionally be used to mount the energy outlet sockets keep watch overled with the aid of the circuit. Note that sockets are female elements.
Let’s simply finish this description with the sole restrict imposed with the help of our circuit — but it’s very simple to agree to, providen the intended use. In order to remain brought about, the solid-state relays must elevate a minimal holding present, which is 50 mA within the case of the instruments we’ve selected. In sensible terms, this just means that each and every of the devices powered by means of our sequencer should draw as a minimal 50 mA, or in different phrases roughly 12 VA at 230 VAC, or 25 VA at a hundred and twenty VAC.
Author :Christian Tavernier
