EVSE apart again. I'm not sure how many times this device is going to want to be taken apart before it starts to fall apart but I guess we'll find out. Now I should say that in this video I'm going to be messing around with mains voltages which can be extremely dangerous so please don't copy what I'm doing. I mean I'm 60 years old I've had a good innings so if I make a terrible mistake well it's my fault isn't it? But if you're young and beautiful then I would definitely steer clear of doing things like this. So fair warning given and I'm going to actually make this as safe as I can. I'll explain in a moment. So the idea here is that I'm going to connect this which is a light bulb holder onto the live and neutral outputs of this unit and that's so that I can see when this device turns its relays on and when it's supplying mains to the car which will just be a little terminal block in this instance. And I'm also going to try and simulate what's inside the car to a certain extent as far as I can to see what this device does and whether it thinks it is connected to a car. So let's put my lamp holder through the gland or grommet and attach it to the live and neutral blocks on here and then I'll find a bulb that I can put in there. Now the other two connections that I want access to and I'm going to use one of these wires which I made up some time ago actually for the lighting in my shed 12 volts. Well these two connections have only 12 volts on them so let's put them in there. Now which do I use for

Control Pilot and which do I use for Protective Earth? The original wiring had black going to Control Pilot but red on Protective Earth? Yeah not so sure about that. Right so that's my wiring I've put red on Control Pilot CP and black on Protective Earth. So I'm just going to put the back on this thing so that I can flip it over and we can see the display and then we'll try and work out a way of making this think it's connected to a car. Now Control Pilot and

Protective Earth I'm going to connect to this terminal block so that I can connect additional things to that. So let's put Protective Earth up there and

Control Pilot down here. So for additional safety I'm going to supply mains to the EVSE from this power bank. It's only capable of 200 watts output.

Now that can still kill you if you put one hand on live and the other hand on neutral that will pass across your chest. So it can still be dangerous but it's safer I reckon than putting in full-strength mains from a household socket. So let's connect that up and see this thing come on. So the EVSE has come on. Now Control Pilot and Protective Earth should be galvanically isolated inside this unit from mains. So I should be able to touch those and I can that's absolutely fine. So this should be safe to work on to try and pretend we've got a car connected to this EVSE. Now currently the lamp is not on. I don't know which way this switch goes but certainly mains is not being put through to the lamp. So the relays in the EVSE are off and that's because it's saying plug this thing into a car I can't see a vehicle. So we now have to try and put something on here such that this thinks it's connected to a vehicle. And I've printed out this from the Wikipedia article on J1772 and come on! Ignoring

Proximity Pilot for the moment because we know that the wire inside the EVSE connected to the Proximity Pilot pin doesn't go anywhere. It's been cut off so we can ignore all the stuff on the PP pin. But the Control Pilot, this pin 4, goes into a diode and down through a 2.74 K resistor to ground which is protective earth. So if we put a diode and a resistor 2.7 K, I haven't got a 2.74, across those two connections then will the EVSE see this as a car? There is also the option here to switch in a 1.3 K resistor via this relay but we'll come back to that later. Right diode and 2.7 K resistor and I'm going to be really lazy here and just twist these together which I know is really naff but I just can't be bothered to get the soldering iron out so let's twist those together and then I'll connect these to my terminal block and we'll see what happens. Let's actually do this sort of live as it were. Put my finger on there.

Switching between standby and connecting and the lights, if I take that off, the lights are blue in standby. If I connect that, and of course I'm putting a different resistance on this with my fingers, but it does say connecting. I'm not sure whether it's actually turned the mains on yet. I don't think it has.

No, not yet. Now I was just wondering whether this device would time out. I've got my diode and resistor on there permanently. Will this time out if it doesn't see whatever it needs to see to go into charging mode? But it doesn't seem to be timing out. It seems quite happy to wait there and I think the next stage of this is to close this relay as it were and put this, is it 1.3 or 1.2? I think it's 1.3 K there. I'm not sure if I've got a 1.3 K resistor and put that also across, yes it's switched to ground isn't it? So also across this resistor thus pulling this voltage down even further. You see this voltage 12 volt is sourced here, 12 volts. It goes to a 1 K resistor. So by pulling it down through this diode with a 2.74 K resistor, we pull the 12 volts at this point down to about 9 volts and that indicates that the car is connected. So it says connecting. Then the car should respond by closing this switch with an additional resistance further pulling this voltage down from 9 volts to 6 volts and that's probably what will trigger the EVSE to switch on the mains and then this bulb should come on. Well I don't have a 1.3 K but I do have a 1.2 K so let's put that across this resistor and see what happens. And yes it's gone into charging. Now my lamp hasn't come on. That's probably because of that switch.

Let's try again. There it is. The mains is being sent right through this unit and to the car or in this case that bulb because it can see now that the control pilot signal, the top half of it, and that's the function of this diode, it only pulls the top half of the 1 kHz square wave down to 6 volts and that puts it in charging mode. I take that away. Oh it says end. Okay now let's try a couple of things. I'll turn off the mains which I can do on my power bank. Now what happens if the mains comes on to the EVSE with the connector plugged into the car so it should be seeing this diode and 2.7 K resistor.

Turn on the mains. The EVSE comes on in standby but then fairly quickly goes into this connecting mode so it doesn't seem to matter if we have this pull down to 9 volts. Remember it's only pulling down the top of the waveform to 9 volts.

The minus 12 part at the bottom of the waveform, and I'll get a scope in a minute, remains at minus 12 volts and I think the idea of that is so that if, I don't know, your type 2 plug was lying in a pool of water and there just happened to be 2.7 K between Protective Earth and Control Pilot, it's unlikely but it could happen, seeing this asymmetry by virtue of this diode means that it's not going to turn the mains on when the connector is lying in a puddle. So now I've connected both resistors in parallel so that we're pulling the top half of the square wave down to 6 volts and it's turned the mains on. Let's turn off the supply to the EVSE so that that drops out and see if it's happy to see this situation immediately it powers on. Put the power on the EVSE, standby and yeah it goes straight into supplying power so the relays have closed and it's supplying mains power to the car so it doesn't seem to mind, there doesn't seem to be any kind of sequencing required, if the conditions are satisfied it just gets on and supplies power to the car. Now one thing I wanted to test, if I short out this diode with a crocodile clip cable then we're going to pull down both the top half of the square wave and the bottom half, will it detect that there is then symmetry on the pull down? No it doesn't, it doesn't seem to care whether the diodes... I'm not sure whether this crocodile clip is any good actually, perhaps I'll try another one. Well let's try this again in the connecting state so my second resistor is disconnected, let's see what happens if the diode is not there and no it doesn't seem to care about that, so it doesn't seem to be taking much notice of whether or not that diode's in circuit. I'll just get another croc clip because I can't be sure this is a good one. Right I've got a new crocodile clip lead, this one's got an S on it which means I've soldered the wire to the crocodile clip because the crimped ones can be quite bad and the little C there means that it's high current, I've got a decent piece of wire on there. So why isn't it going into... oh it's gone into end mode, oh that's interesting, yes but if I put the second resistor across there it immediately goes into charging mode. It's saying end rather than connecting which is slightly odd. Okay let's make it conduct and now short out this diode. No it doesn't seem to care whether or not the pull down on the square wave is symmetric or asymmetric. I think it's time to get a scope and have a look at the square wave on here. So here's my scope hooked up and I'm having to use this additional light here otherwise it bleaches out the screen of the scope, it's just an exposure compensation thing. I suppose I could do that on the camera but never mind I've done this now. So we can see that it's exactly one kilohertz, the width of the pulse is about 10% which is what you want for 6 amps, you can see 6 amps there and if I press the current button in this end state I can actually vary the current so 8 amps is more than 10% that's 10 amps, 13 amps and this one goes up to 16 amps. I can't remember the percentages just at the moment let me check. Right I've done the exposure compensation on the camera now. Oh it's not quite as good is it? How do I adjust that? No that's not working terribly well.

It's also put a thing up on my screen so I can't see very well but never mind. So yes you can see I can press the current control button and that just varies the pulse width of this waveform. So let's go back to 6 amps that's a 10% pulse width.

Now if I close this second resistor which turns on the relays the other thing you can see is that the height of the positive part of the waveform drops to 50% from 75% so 9 volts down to 6 volts but the bottom part of the waveform is unaffected and that's because of the diode. So let's now see what the effect of putting my shorting link across the diode is. I'll hang that resistor over there permanently to turn on the mains. Let's short out the diode.

Yes the scope should be right with that shouldn't it? And yes you can see there that the bottom part of the waveform is also reduced in amplitude as well as the top but that doesn't seem to be noticed by the EBSE.

Oh why's the screen gone all funny like that? I don't know. Yes I think when this was intermittently contacting and we were glitching the mains on and off like that I think it interfered with the signal going to the display and that went funny. It seems okay now. So yes it's simply a case of a diode and two resistors one to pull the signal down to 9 volts and another one to pull it down to 6 volts that initiates the charging turns on the relays and actually supplies mains well in my case to the bulb but there doesn't seem to be any sequencing required you just simply put the resistors in and even if both resistors are in when you power up the EVSE let's just try that power it down power it up then very quickly it just goes straight into charging mode so no sequencing required it seems. Now something else I wanted to try which is can I change the current while it's in the connecting mode we've seen that I can change it while it's in the end mode whatever that means so that's 16 amps let's turn off the mains turn it back on and see whether I can because it'll go straight into connecting mode because it's got the diode and resistor see if I can change the current now and I can so now let's put it in the charging mode with the second resistor my mains lamp comes on and now pressing the button I can't change the current so as it stands this EVSE wouldn't be able to have the current modulated by for example the amount of solar power coming off my roof while it's charging because it simply doesn't respond to changes in requested current or maximum current while it's in the charging mode you'd have to come out of the charging mode which would be not a very nice thing to do change the current and then go back into the charging mode which is not ideal really and as we've seen this particular EVSE doesn't seem to care if you short out the diode and just have the resistor and then put a second resistor on there it doesn't seem to care whether this signal is pulled down symmetrically or asymmetrically it connects the mains regardless not sure that's ideal really so there we are all you need to make an EVSE think that it's connected to a car is a diode and a resistor and then another resistor to tell it or for it to think that the car is actually charging it's as simple as that cheerio