EasyEVSE Build (part 1)

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Testing the relay drivers and looking at schematics for the control pilot circuitry. Big thanks to Bernhard Walter for letting me share his AnalogEVSE project.
AnalogEVSE webpage and schematic:
www.analogevse.xyz/AnalogEVSE-...
www.analogevse.xyz/analogevse-...
Other datasheets:
en.wikipedia.org/wiki/SAE_J1772
omronfs.omron.com/en_US/ecb/p...
www.hlktech.com/en/Goods-14.html
e2e.ti.com/blogs_/archives/b/...
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(We each get £50)
#EasyEVSE
#ElectronicsCreators

[@sdgelectronics]

Watch out for those DC-DC converter modules, they're not regulated and can drift quite a bit with little or no load. Moving forward, you could reduce voltage on those relays once they're held in. Full current is only needed initially, but you may be able to drop it to 60% after that reducing power consumption considerably.

[@JulianIlett]

Yes, I vaguely remember the B1212S having an unusually high output voltage. If its a problem, I'll load it down with an LED.

[@sdgelectronics]

@@JulianIlettled works for me 👍

[@romancharak3675]

I reduced the current consumption of some relays with a pwm signal, once the switch has time to close (say 1 second). But, the pwm signal had to be above 20 Khz @ 50% dutycycle, otherwise I could hear the coil resonating. I sure there are other ways to reduce coil current. Latching relays are another solution.

[@David_11111]

yay this project is really cool :)

[@UpLateGeek]

I think the comparators I'm using in my current project are the TS374. I wanted a very low input bias current and fast response time, although they're probably not that critical with my design. I don't think they'd work in your application though, since you need the input to go down to -12V, whereas the TS374 only has a maximum voltage range of 16V.

[@andymouse]

Thats cool ! greater than or equal to 250mA max so the sky's the limit, nice circuit walkthrough...cheers.

[@fredflintstone1]

Gouda Cheese!!!!!!!!!!!!!!!!

[@andymouse]

@@fredflintstone1 SQUEAK !!!!!!!!!

[@jamess1787]

Part 2! Part 2! Part 2!

[@markflack9191]

What happens if your circuit does not switch off the relays at boot up. as you have it as soon as the 12v line is there the relays will pull in, unless they get a signal not to, should your relay drivers be biased off and pulled high to switch on power.

[@JulianIlett]

Good point. The -12V peak detector would appear to prevent the relays glitching on on startup. I'm not going to bother checking the -12V level on my first build, so the relay glitch may happen. Let's see :)

[@laurawerner]

I came here to say the same thing. It seems potentially unsafe to have the relays close (and deliver mains power to the plug) if 12v power is lost, if the Arduino crashes, etc. It's probably better to have the transistors pulled down by a resistor and actively pulled up only when the Arduino wants to switch on the relays.

[@CollinBaillie]

So, the EVSE has 2 functions: 1. Detect presence of the vehicle, and switch on the AC supply 2. Generate the 1kHz signal that tells the car how much current it can pull And the car does all of the AC/DC conversion and current limiting. Is that correct?

[@JulianIlett]

I'd re-word that slightly: 1. The EVSE detects the presence of the vehicle (CP drops from +12V to +9V) and enables the 1kHz square wave to signal how much current the vehicle can pull. 2. The EVSE detects the vehicle's readiness to charge subject to the requested current limit (CP drops further to 6V or 3V) and turns on the relays. The car's onboard battery charger draws mains current (limited by the CP signal pulse width) and charges the battery. It may also perform charge scheduling, cell equalisation, and (on my car) V2L functionality.

[@denisouellet6518]

Correct, but there's also a ground fault (GFI) protection (making sure the current in Line is returning to the Neutral) and some AC or DC current leaking to the Ground as well. In some EVSE, you can have some overcurrent and over temperature protections too.

[@DreStyle]

AHH still using the flashlight haha awesome ...I miss the post unboxing vids alot

[@joruss]

You don't need full holding current if you won't be kicking relays mid operation. I think you can still reliably drive it with 10v instead of 12. Should save you some power. But I guess the easiest route is to just beef-up on power supply.

[@JulianIlett]

Yeah, I think it would be easier to put in a bigger PSU than extra circuitry to drive the relays at 2 different power levels.

[@fredflintstone1]

I am suprised that you chose such a low output PSu unit maybe a simple 12Volt 1amp pcb charger may have been a better choice in retrospect ( damn I am sounding like Capt hindsight )

[@BenMitro]

I was expecting that you measured the holding current of the two relays while powering them on directly?

[@MattWells0]

Why do you need 2 relay control circuites? Given that you want both both relays going on and off at the same time wouldn't 1 relay control circuite be enough?

[@JulianIlett]

Just wanted to spread the relay current across two transistors. Not sure it was entirely necessary.

[@FoolishDane]

I haver never seen anyone put a capacitor across the relay coil and I seriously doubts that there is any benefit to it. In fact you could end up destroying the transistors because of the inrush current.

[@dogastus]

I was going to say the same thing. It won't stop contact bounce.

[@jameshancock]

Why wouldn’t you use a triac and save the space and increase reliability?

[@iamdarkyoshi]

lol you call that a granny charger? Here in the states, my car defaults to 8A when using the granny charger (or 12 if I manually request it every time I plug in) But at 120v instead of 240v It's so slow!

[@CollinBaillie]

Julian described this name in a previous video. It's "the type of charger you use for your vehicle when you go to visit Granny" Ie regular mains is the only available source, likely because "Granny" hasn't gotten into this fancy new EV stuff. Colloquialisms can be amusing!

[@sdgelectronics]

@@CollinBaillie I think it's granny charger just because its slow

[@gordanmilne7034]

Not all grannies are slow or old.

[@CollinBaillie]

@@sdgelectronics Careful! We don't know if Julian is a grandfather or not! 🤭 He legit offered the above explanation in his first EVSE video in this series.

[@sdgelectronics]

@@CollinBaillie I did see that video, I'd just heard differing opinions on how the term had been coined 🙂

[@helmuthschultes9243]

Not confident to use one transistor to drive both relays? Surely the relay windings would draw well under 200mA, so driving up to 400mA should easily be handled by a TO92 transistor, there are plenty rated even beyond 800mA.

[@David_11111]

why not just cut the spades off, as they are pined to the bottom also !!!!!

[@helmuthschultes9243]

Should be no doubt that the Hongfa is a vopy of the Omron. There are almost no original Chinese designs.

[@JulianIlett]

Although the Omron relays say 'made in China' on them.

[@helmuthschultes9243]

@@JulianIlett that Omron manufacture in China is keeping product cost low. But Omron design, and test their designs while many Chinese companies manufacture des8gns by the likes of Omron, Honeywell, Bosch, and other reputable engineering organisations, rather than design own relays ( or other products for that maaltter). Making compatible substitues does NOT mean making a copy of the design of other reputable manufacturers. These copy desgns also often fail the quality and features, havinf internal hidden cost cutting or other quality deficiencies, while externally looking ixentical expect brand name and even superficial internal build identical appearace. Cheaper contact materials , weaker springs not ensuring firm contact pressure, lack of wipe action of contact, and more, leading to endurance issues and contact wearout, oxidation, burnout/overheating. All too many China branded parts/components are stolen designs that many times are visually identical, lower price, but then fall short of being truely equivalent. They make huge profit without the engineering costs, investment in design/research, and finally even in manufacture.

[@alankingvideo]

Why dont they buld this into the car and give you a long fat kettle lead? what a load of faffing about.

[@JulianIlett]

Safety, mainly.

[@alankingvideo]

@@JulianIlett it's Electrical correctness gone mad! I want one on my camper van, and my 10 amp double hot plate.then, and one built into all Grannys.