# Diode help



## evmetro (Apr 9, 2012)

I am needing a diode to place between contactor "B" negative and relay #3 (labeled "r3" in my drawing.) When I plug in shore power to AC DC "B", I am getting 12v back feeding through the coil on relay 3. The purpose of this circuit is so that I can plug in 220 on one plug and not read 220 on my 110 plug that is run in parallel. I have male pins on both my 110 and 220 plugs, so I want to isolate them from each other. I also want to be able to make the dumb mistake of plugging in both charge cords at the same time. I can only have one contactor open at a time to be safe. The AC DC converters are wired directly to the charge inlets so they come on when you plug in.
Anyway I am not educated in diodes yet, but I am going to pick some up at radio shack or somewhere and was hoping somebody could tell me how to pick out this diode... Part number or specs or something...? Thanks


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## major (Apr 4, 2008)

evmetro said:


> I am needing a diode to place between contactor "B" negative and relay #3 (labeled "r3" in my drawing.) When I plug in shore power to AC DC "B", I am getting 12v back feeding through the coil on relay 3. The purpose of this circuit is so that I can plug in 220 on one plug and not read 220 on my 110 plug that is run in parallel. I have male pins on both my 110 and 220 plugs, so I want to isolate them from each other. I also want to be able to make the dumb mistake of plugging in both charge cords at the same time. I can only have one contactor open at a time to be safe. The AC DC converters are wired directly to the charge inlets so they come on when you plug in.
> Anyway I am not educated in diodes yet, but I am going to pick some up at radio shack or somewhere and was hoping somebody could tell me how to pick out this diode... Part number or specs or something...? Thanks


That is difficult to follow. In fact, I can't. The use of standard electric schematic symbols would help me. But I got to ask: Why not just use the standard EV plug and receptacle? It would eliminate those 10 extra components and associated wiring, improve safety and improve reliability/durability.


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## evmetro (Apr 9, 2012)

Major, thank you for looking at this diagram. If it would help to read my diagram, here is a the AC circuit that is associated with it.










Here is how these relays work: Pins 1 and 5 here activate the coil, pins 3 and 4 are connected when the coil is NOT active, and pins 2 and 4 are connected when the coil is active. In my original diagram in the first post, (the DC part of it) you can see that the orientation of the relays is the same as the below illustration.


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## evmetro (Apr 9, 2012)

Major, I am interested in improving my schematic drawing skills. In the beginning, I was wiring stuff with no diagram at all, and Frodus was able to make me see the light on the importance of drawing diagrams. Now I have diagrams for everything. The the reason that these relays are represented the way that they are, is that this is what the pin orientation looks like when I look at the actual relay. Perhaps I can adapt to something more official. 

You asked why I am not just using the J plug? We may never agree on plugs, but I have noticed that one of the most popular things that comes up when a new guy comes to this site wanting to build an EV: we need to know what his specific needs are. Some people may work where there is a J charger, but for me, all I see is my 50 amp circuit at my shop, and a 110 plug at my home. Since there is no J station in my life, my specific needs dictate that I adapt my EVs to the existing power grid. The reason for this circuit that I am using is to make the versatility of having two charging inlets safe. We know that the male end of extension cords, 220 or 110, plug into the wall, so this means that whatever device is plugged into the female end of extension cord needs to be male to fit the female. Not a problem for a single charging inlet, but since the two plugs that I have chosen are male and they are in parallel, the second charging inlet would be a hazard with live male pins. This circuit is designed for safety, but also from an engineering perspective, it contains the safety circuit to the car and not the AC power source. Another one of my specific needs is simplicity, and I am not ready to use a special cord to plug in my car. I have been plugging things in for a very long time with a traditional extension cord and have gotten very used to this. I also enjoy privacy and don't really want to have my electricity usage monitored or governed.


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## TEV (Nov 25, 2011)

Hi, I will not comment of your diagram or functionality, but in order for you to get an answer to your question, you will have to specify the contactor specification regarding it's coil (amps rating) .


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## evmetro (Apr 9, 2012)

When I test this circuit in the car, I plug in 220 charge cord, so AC DC "B" comes on and sends 12v DC to relay 2. Relay coil 2 activates and allows 12v DC to flow to contactors A and B, and relay 4. Nothing should happen until a ground is provided by the switch between relay 4 and the Orion. I am using the switch in the chassis ground position for testing, but once this thing is on the road, I will rely on the Orion to provide the "ground" signal. (It is actually a digital drain) Anyway, the problem that is occurring here is that when the 12v reaches contactor A, it flows through the coil on contactor A, through the coil on contactor B, and into relay 3. This is where the problem starts. 12v backfeeds enough to go through relay 3 coil and into AC DC "A". Contactor B coil does what it is supposed to do and the contactor connects the AC like it should, but when I use that switch to remove the ground, contactor B does not disengage. I am assuming that I need a diode between the coil of contactor B and relay 3 that blocks positive from reaching relay 3 but still allows the negative from relay 3.


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## evmetro (Apr 9, 2012)

TEV, is there a way to determine these specs with a multimeter? Not reall sure how to find this info out...


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## TEV (Nov 25, 2011)

evmetro said:


> TEV, is there a way to determine these specs with a multimeter? Not reall sure how to find this info out...


All you have to do is to get a reading of the Amps of the coil when activated with 12V. You need that info in order to get a proper size diode . If you read under 1A you can use an 1A or 1.5A diode.
I think that any "general purpose diode" will do it , anyway, in order to someone more skillful in electronics to be able to recommend you a diode , the information about your contactor coil amps rating will be needed.


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## evmetro (Apr 9, 2012)

I am fascinated with the gap between the layman and the EEs. The layman is unable to communicate the essential info to the EE, but the EE is unable to interpret the simple info from the layman. What I will have to do is go down to radio shack and pick out a handful of various diodes to play with until I find one that works. I just thought I could get a few pointers before I went. TEV, your input was the srongest in this matter, so thanks very much. I know that my AC DC converters are only 1.2 amps, so this will probably narrow down my trial and error testing.


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## TEV (Nov 25, 2011)

evmetro said:


> I am fascinated with the gap between the layman and the EEs. The layman is unable to communicate the essential info to the EE, but the EE is unable to interpret the simple info from the layman. What I will have to do is go down to radio shack and pick out a handful of various diodes to play with until I find one that works. I just thought I could get a few pointers before I went. TEV, your input was the srongest in this matter, so thanks very much. I know that my AC DC converters are only 1.2 amps, so this will probably narrow down my trial and error testing.



I have a " wireless advisor " for my elithion lite BMS, until last Sunday was powered only when the ignition was ON . It's needs a 12V @ 0.2A power source, last Sunday I installed a [email protected] 0.5A power supply wired on the charging port , I didn't want to use a relay to separate the 2 12v sources going to the device so I did a separation using 2 diodes. I was having the same dilemma like you "what diode to use ?"
I have a circuit board , I think is from a satellite receiver, and it has some diodes on it , I choose the one being in a group of four thinking that those will be the rectifier diodes, the part number on them was 1N5399 , a minute on Google and I find that they are "1.5A general purpose diode" remember, my device is only 0.2A rated, so I was satisfied. 

It's very important to use a diode with an Amp rating higher than your contactor rating otherwise the diode will overheat and fail.

The 1N4001, 1N4002, 1N4003, 1N4004, 1N4005, 1N4006 and 1N4007 are rated for 1A.

So, before you can start lookin for a diode you need to know the contactor coil rating.


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## palmer_md (Jul 22, 2011)

The problem you have is that the Orion ties both sides together. You need to separate the power prior to the Orion getting any. In order to do that you need different components. I think you could probably use a diode to make it work, but it would be better to use different components.

Here is an example solution. Two three pole contactors with an auxiliary normally closed contact. These have a 120vac coil instead of the 12vdc coil you currently have in your diagram. The charger gets power from points A,B,C on the two relays which get tied together on the charger. (actually I just noticed that the diagram is wrong. the 240v ABC should actually be ACB so that they join correctly on the charger.) Your universal 12vdc power supply can be powered by A&B, and it can power the Orion, and your interlock signal can be a 12v relay with two normally open contacts that get installed as shown. The BMS would then close these contacts if it is ok to charge. If the BMS is not working, they will open up and will not allow the charge. If the 12v power supply dies, the contacts will open and stop the charge.

In this setup, the first one to plug in "wins", and the other port is disabled. You will not have any power "back-feeding" on the opposite plug port on the car.


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## evmetro (Apr 9, 2012)

I just got lucky. I went to radio shack and bought these:










The first one that I tried worked, and here it is if anybody ever wants to replicate my circuit...










I ended up having to place it between relay 1 and relay 3. No more angry relays, the circuit works beautifully! I tried both plugs and only one contactor opens at a time, and I plugged in 110 and 220 at he same time. still only one contactor.


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## evmetro (Apr 9, 2012)

Palmer, thanks for checking this circuit out. I am still studying your diagram. Relay 2 in my diagram switches between AC DC sources, depending on which AC source is being used, so that only one of the AC DCs can power the Orions ready power at a time.


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## palmer_md (Jul 22, 2011)

evmetro said:


> Relay 2 in my diagram switches between AC DC sources, depending on which AC source is being used, so that only one of the AC DCs can power the Orions ready power at a time.


Yes, but then you are switching both relays from that same power which is why you were getting power back-feeding the opposite relay. Diode stops the back-feed, but I prefer a more separate solution. Given that you already had the entire circuit built, I'd have probably just put in the diode like you did, but for future builds, I'd keep them more separate.


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## evmetro (Apr 9, 2012)

Palmer, I don't fully understand your diagram yet, probably for the same reason that Major doesn't understand mine. I will need to learn what the symbols mean. Would your diagram still allow the appropriate AC DC to power the other 12VDC circuits? I use this AC DC power supply to power relays for this "charge safety" circuit, but I also use it for bluetooth, wifi, charge enable, water cooling and other stuff while in the charge mode. Most of my charge mode circuits are negative or digital drain, but I also use a bunch of positive triggers...


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## palmer_md (Jul 22, 2011)

There is still one power supply in the diagram. I have it in the bottom right. It is powered from wires A and B which connect to both contactors which one of can be closed to provide the power. If you need more 12v power you can still power them both from wires A&B.

I did not show wires A, B & C on the diagram because it was going to make the little paper I used very busy, but simply connect all the like letters together.


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## evmetro (Apr 9, 2012)

I think that I follow the diagram now. I have a separate charge enable circuit that tells the charger that it is okay to charge or not. How would I shut these contactors off when the Orion takes away the ground signal? This is how the Orion stops AC from reaching the charger. The interlock that stops me from driving away while plugged in comes from the 12v signal from the AC DC. It has seperate inputs for 12v charge power and 12v key power. This is why all the outputs are negative triggers.


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## palmer_md (Jul 22, 2011)

The Orion BMS would trigger the double pole relay that I have on the left side of the diagram. BMS would pull in and close those contacts to allow either 120v or 240v charging. If the BMS wanted to terminate charging it could remove the enable signal and power would be removed from the charger.

edit: of course after writing this I found an error in the wiring logic. If the BMS removes power then power is also removed from the 12vdc power supply. Also the BMS would not be able to power the contacts closed without power, so this wont work unless the BMS gets power all the time regardless of if you are plugged in or not. If you are not powering all the time and are relying on the universal power supplies to boot up the BMS then things get messy again. You could just add a third contactor, to replace the shown BMS contacts, and have the feed to the power supply on the feed side and the discharge side goes to the charger. This would allow for the charger to get disconnected and leave the main interlock contactors alone.


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## palmer_md (Jul 22, 2011)

evmetro said:


> Palmer, I don't fully understand your diagram yet, probably for the same reason that Major doesn't understand mine. I will need to learn what the symbols mean.


There are several versions of accepted symbols, and you can google electrical symbols if you like. The relays we are discussing can be found here. http://en.wikipedia.org/wiki/Relay There are other ways to represent them, so there is not an absolute standard, but the diagrams you have are very hard to follow since they were not like any standard that we know of. Your added information about the location of the coil and the normally open and closed contacts helped me to decipher the drawing, but without that it was nearly impossible to understand it. 

Glad to hear you got it working. Awesome conversion by the way. Looks even better in person, and I can't wait to see it in the sunshine some day. Absolutely stunning paint and body.

Also the other method that could be used would just be an adapter for the 120v into your 14-50 plug, and this would have avoided the relays and all the other logic all together.


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## evmetro (Apr 9, 2012)

I found some pretty cool sites that show the symbols. I suppose I assumed that since this site is about diy "electric car" and these relays are "standard automotive relays"", that everybody here would just automatically know what they were. The illustrations showed what they look like when you hold them in your hand. This type of diagram may still be more useful to the layman diy guys if they want to replicate a circuit from a diagram. I find that this kind of diagram makes it much easier when I am stringing wire since the relays look just like the diagram. My aim here is to remain bilingual so that I can communicate with an EE, but still be able to translate that stuff to the hobbiest or layman. Palmer, it was pretty cool having you drop by the shop. I have been lucky enough to have onegreenev drop by a couple of times as well. There are not many of us EV enthusiests around, so it is a pleasure to know the few.


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