Good morning all i've completed the assembly of the minimalist version of analog evse. Now that's a project by bernhardt valtter, i'm going to put a link to it down in the description below you can go and have a look at that. This is a cut down version of it, which i'm hoping will do just the essential functions that will turn this into an electric vehicle, not charger exactly but an electric vehicle supply equipment. So let's get straight into powering this up, so i've got my battery 12v battery.

Here, let's put positive on there and negative on here, and one of the things i want to know on initial power up is: is there a little relay clack? In other words, do the relays briefly pull in which could briefly put mains on a connector which you could potentially have your fingers in you'd be pretty dumb to put your fingers in it, but do they clack, let's find out no nothing at all. So the relays remain uh open when you put 12 volts onto this circuit right. Let's take a look with the scope at some points, so in the previous video i had the square wave generator working generating my one kilohertz square wave. Let's take a look at that i'll press auto on the scope there it is the trigger is in the middle.

Oh, it's slightly lopsided now, because it's driving through a 2k2 resistor a 100 end cap. So yes, there's a little bit of rise time and a little bit of fall time. Let's look at the top end of that cap, which is there and now we can see - and i can probably take that up. Um this triangle wave and, of course it's not a precise triangle wave.

It has a right, a capacitor-style rise and a capacitor-style full, but the point is: if you put that into a comparator against a fixed voltage and you move that voltage up and down, you will widen and narrow the resulting pulse uh. Can we take a look at that that be the output of the first comparator? Won't it, and that is here there um. I think i'll have to bring the well i'll just press auto again, so that is um. The comparatored uh triangle wave and we've got a narrow pulse now the question is well, the frequency is one kilohertz, but the question is: what is the width of that pulse? Well, it's two divisions where they're 50 microseconds slightly more, possibly so it's about 100 microseconds.

So we've got 100 microseconds of on time and 900 microseconds of off time. That makes uh one millisecond, which is the equivalent of one kilohertz. It's the period version of the one kilohertz frequency. So next um now move on to the actual cp signal itself, which is down here.

If i just poke it in that hole there, and there we've got with a 23.7 volt swing um our 10 pulse width now 10 corresponds to a 6 amp charge, which is about, i think, 1300 and something watts at 230 volts. Now the voltage, which is the top of this waveform, is measured with the peak follower and that gives you a static dc voltage. I mean there's a slight movement on it. Oh, i triggered something there um, but that's measuring all just over 10 volts.

I think, because there are two diode drops one in the emitter follower and one in this four one. Four eight, i think i said it was going to be something like 10.8 volts. Well, it's not far short of that and then that peak voltage is fed through to the comparators and depending on what that voltage is now. If that voltage is between 7.5 volts and 1.5 volts, these relays should turn on, but the only way we're going to get that to happen is, if i put a resistor, which is what the car does across this output.

Now i'm going to put a 1k resistor, because that creates a potential divider, the 1k resistor, that's on the back end of the line driver and this 1k resistor should bring the cp line or the top of it down to six volts, and that should turn the Relays on so, let's look at the cp pulse there. It is we'll bring it down to six volts and the relays turn on. If i can get a good connection on my 1k resistor now, you'll notice that it comes down both the top comes down and the bottom pulls up if we put a resistor with a diode in series with it. That won't happen.

In fact, why don't i make one so in the electric vehicle is actually this: it's a diode and a resistor um, and when the car wants to pull some charge, it brings the resistor down to 800 ohms or something like that. Well, this is 1k. It's quite close, so let's put that and look at the waveform, and if we put that on there, that's the wrong way around. Isn't it because that's pulling the bottom up, but not bringing the top down of course, cp's down here.

Isn't it yeah protective earth? Is the top point so that brings down the top of the waveform but doesn't bring the bottom up, but since we're only looking at the top of the waveform for our comparator measurements, that is sufficient to pull the relays in now. If we put a resistance across here, which might be like someone putting their fingers across the exposed pins of the connector, we should see, of course, that the reduction in waveform height will be symmetrical. And if i had the additional comparators in this circuit, the relays shouldn't actually respond to this. They should reject that as an error and only close the relays if the top comes down, but the bottom doesn't go up, but i haven't built that circuitry, so it works in both instances with just the resistor or the resistor and the diode.

So, let's just go through this schematic and cross out what i didn't build. Well, i didn't build that. I didn't build that all that all that all that, so yes only three comparators these two, which are a window comparator and this one which cuts this triangle wave down into a narrow, pulse width square wave. And i linked across there joining the line driver for control pilot directly to the output of this comparator.

So that's what i built quite a simplified version really now i must admit um when i first looked at this schematic. I couldn't quite work out what this capacitor was doing. It's in this resistor divider chain, which provides these voltage references for the comparators, but it's a very large value. One microfarad and i thought that's a bit excessive, just to stabilize this voltage and also, why aren't there stabilizing caps on the other voltages? But i don't think that's what this does.

I think what this is is a power on slow rise capacitor. So i think the idea is that v con comes up slowly and that could alleviate a possible problem where, when this hundred n charges up uh as this 12 volts comes up, when you first power on, you will take the voltage on the top of this capacitor. Through the comparators window - and you will very briefly energize the relays but i've since looked at this - the time constant of this 100 n with a 1k driver - is something like 100 microseconds uh the time constant of the relay, or we can look at the datasheet. For that um it's got a 20 milliseconds uh operate time and a 10 milliseconds drop out time, so 100 microseconds and 20 milliseconds we're 200 times too quick for the relay to pull in briefly when this thing powers up so i haven't, got a problem with it: Clattering, the relay and briefly putting mains on the output pins when it powers up.

So i'm not going to worry about that capacitor, so other things i've been doing. I cut this, which was a six-way connector block cpc didn't have any four-ways. I cut two ways off by pulling these connections out and just hacksawing the end off, so i can now stick that in there, so i might as well do that right now. I think i'll change bits with this i'll use this uh large bit with a big fat chisel, is that a chisel or a wedge one of those two on the end uh right? Let's get that one warmed up, we'll get it nice and hot yeah.

That's smoking away nicely uh. So let's raise that up to 400 and try to attach this thing. Oh yeah, that's soldering in quite nicely. Let's do the far end first and there's a good surface area match to the iron.

That's working really! Quite well! That's done now to vary the pulse width and therefore the current at which the car will charge um. You need to vary this resistor here. So there's a 10k pull up to 12 volts. There's a 56k pulled down, so there's a potential dividers a little stabilizing cap.

There this is ground and um bernhard has put this. He said for fixed current install rv1. I think actually that's wrong. I think it means for variable current install rv1 an omit.

This fixed resistor also put the connector on um for fixed current. You don't have the pot, you have this resistor and then you can add additional resistors on this external point. Now i haven't implemented any of that. My resistors just buried in there somehow but he's handily given this table and for six amps there's no additional resistor across that 56k, so i've just put the 56k in and we do appear to have approximately a 10 mark space ratio so um.

If this thing has 12 volts on it, and it will uh once i put this mains to 12 volt power supply in the board and the fuse, and this connector and put mains on there, um it will given the correct resistance on the output and the car. Will do that of course turn the relays on and let that mains transfer to the car and, at the same time, put out this 10 percent 24 volt swing either side of protective earth uh one kilohertz square wave, which the car should accept as an instruction to Just pull six amps and i i've preset this to six amps and it probably won't change from that because i just want to charge the car at its minimum charge current so that i don't stress, oh got ta be careful flipping these over. I don't stress uh. These live and neutral tracks too much.

I i still need to put um tinned copper wire along here and solder it down. So we've got a nice high, current mains transfer area. Now the um capacitors here which sit across the relay coils a couple of people, were saying: it's uh they're not going to do much and the idea was they'd. Stop relay chatter, but i think what i'm going to do is put some leds in these holes so that we can see the relays coming on.

These are those bright green ones, but i don't want to pull too much current from this power supply. So i'm going for 2k 4 as my resistor, just because i happen to find some and yeah that's interesting. I don't know whether you're going to see this, but if i glitch the power, those leds do briefly come on, because there is a very brief traversal through the window comparators on stage as this circuit powers up. But it's not long enough to pull the relays in.

So i'm not too concerned about it. Now, if we put the resistor across cp and protective earth, these two leds light up they're pointing in different directions, but there they are so now you can see the relays coming on. Okay, that's a good addition! I've just been out to the shed and got this real, a very fat, 18 swug, uh standard wire gauge, not sure what that is in our work, american wire gauge, but whatever so i'll cut some pieces of this, lay it down on these tracks and then flood Solder in just to beef them up a bit, they are on the top and on the bottom, but um they're, one ounce, copper, so yeah, let's beef, these up, i can do these two now i'll have to make the second connector in order to do these ones. Right now, i've got to cut this six-way connector down to a three-way connector to put there for the mains input.

So let's start levering these things out i'll take three of these out and then i'll saw this off with a little hacksaw right. That's my three pin connector cut to size so i'll, just tack that in place and then get some more of this thick wire and lead over these tracks, get it all soldered up right, also going to need this fuse holder for the 12 volt power supply and I've just left a little gap there, so i should still be able to get the fuse holder in and soldered yep. That looks. Okay, right here are my high current tracks: i've soldered the thick tin, copper wire onto these traces, so that this is only taking six amps at mains voltage.

So it's not a huge amount of current, but i thought i'd just toughen those up right. A final test before i fit the 12 volt power supply just to make sure it's still behaving itself, because of course, i shouldn't uh put 12 volts onto here when this power supplies in place. That's just a bit naughty right, let's put resistor on across here, and that looks good. So i think it's time to put that power supply in and there it is all soldered up ready to go in the box.

The evse that i bought to replace the circuit board that was in there. Let's do it so here we are. Let's lift this one out: try to leave that in position. Put that over there.

Here's my replacement board in it goes. Will it fit um it's rocking on something probably some of these longer pins, so i might have to snip them down a bit right, mounting screws for the board put that into the box, and then i'm going to have to attach the mains to the input socket. Mmm scary right live to the top one like so protective earth to the middle one which is different to the original layout, but it just worked better with protective earth in the middle for me and neutral to the bottom, one, that's quite close to that zero volt Pin but not close enough that i'm worried, ah something i've forgotten is the fuse. Of course.

I think you can use that slot. Oh, yes, you can to lift the lid. That's good. Let's find, i think, something like i don't know: 500 milliamps or something should work in there.

I've actually found some 250 milliamp uh, quick acting, so that should be fine shouldn't it. I mean this thing's going to take precious little current from the mains. I'd have thought: let's use one of those. Oh yeah.

The wiring here is extraordinarily thin, yeah, that's very thin, but uh that will give me the best safety so i'll put that one in and then to make sure my fingers are nowhere near the mains. When i try the little resistor across the terminals, yes well, when i can get that in there right to test this, i'm going to use the most benign mains. I've got, which is this little 200 watt, pure sine wave inverter on this power bank, so i'll plug that into the commando via an adapter right switch on. Will it go bang, let's power it up? Well, that's the mains on it.

Of course, there's nothing to see until i put the resistor across these two wires, not anywhere near the mains. Am i so? Let's do that and that turns the mains on, and we should also be getting the waveform uh here on the cp line. So we can check that with the scope and so with the waveform. There's the scope on there, let's put the resistor on and that drops down to uh six volts, of course, because of the resistor.

But it's the dropping down to six volts. That's causing the relay circuit to pull in so that all looks good right. I think that's about it for today my workshop's in a total mess. I need to have a bit of a tidy up, but the next step is to connect this to my car.

So when we get a nice day with a bit of sunshine, i will do that and video it, but for today cheerio.