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OEM ECU controlled DIY dual voltage big pump controller

Old Nov 8, 2018, 12:27 PM
  #16  
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Originally Posted by Jaraxle View Post
Your not wrong. Cars are electrical noise crazy! However, the design of using Crydom SSRs for pump control is not something that needs to be concerned with that issue. Crydom relays are top notch, and the pump is directly wired to the battery. I think the design is solid as is, and since the triggers are 3v+ there are no chances of noise causing an unwanted SSR trigger. Thanks for the input, and I certainly don't mind anyone contributing to this little project. A guy at work asked about SELLING this, and I just don't have the energy or greed to drive that...LOL... so it's open source I suppose...
I'm not so much concerned with transients causing false triggers, although that would be a concern. SSR's are fet based and fets fail open so if the ssr fails you lose power to the pump. I get that you like Crydom, but its going to take more then a strong endorsement for me to trust my engine to a device. Nothing in Crydom's material leads me to believe that it can suppress ISO 7637-2 and ISO 10605 type transients. It being hooked up to the battery doesn't make anything better because that's literally the main power rail for the whole car, it will experience all the bad stuff. Crydoms site doesn't list automotive as an application for these devices either, and the datasheet here http://www.crydom.com/en/products/ca...anel-mount.pdf doesn't show any real protection on the control or switching side of the SSR. What the datasheet does show is that for inductive loads you need to add a freewheeling (flyback) diode to the load to protect the device which you haven't done in your setup. So you are going to want to add that for sure.
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Old Nov 8, 2018, 12:45 PM
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Originally Posted by Biggiesacks View Post
I'm not so much concerned with transients causing false triggers, although that would be a concern. SSR's are fet based and fets fail open so if the ssr fails you lose power to the pump. I get that you like Crydom, but its going to take more then a strong endorsement for me to trust my engine to a device. Nothing in Crydom's material leads me to believe that it can suppress ISO 7637-2 and ISO 10605 type transients. It being hooked up to the battery doesn't make anything better because that's literally the main power rail for the whole car, it will experience all the bad stuff. Crydoms site doesn't list automotive as an application for these devices either, and the datasheet here http://www.crydom.com/en/products/ca...anel-mount.pdf doesn't show any real protection on the control or switching side of the SSR. What the datasheet does show is that for inductive loads you need to add a freewheeling (flyback) diode to the load to protect the device which you haven't done in your setup. So you are going to want to add that for sure.
Edit: So what I'm saying is all the big nasty stuff that makes auto electrical harsh is connected up to the battery, its the main rail for the car. The starter, the window motors, the blower motor, windshield wipers, radiator fans, all hooked up to the battery. They are all large inductive loads, every time they turn on and off they send huge spikes into the electrical system. Its because of this automotive electrical has to be designed to be extremely rugged. The standard automotive relay may be crude and slow, but it is very rugged and reliable compared to a complex switching circuit. So if something wasn't designed with protection for these kind of wild electrical spikes in mind it can over time or immediately damage the electronics. It's ok if you want to use something not designed to handle this kind of stuff, you just have to add parts around it to protect it.
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Old Nov 9, 2018, 06:54 AM
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Biggie Biggie Biggie I didn't see, sometimes your words hypnotize me... Your RIGHT!. I thought the SSR had internal protection for flyback.
I am thinking that the VFT2045BP that I already have (and am using in the current circuit), would be fine for a kickback diode on the motor.
Do you concur with that diode selection for protecting the SSR ?

Nice catch!
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Old Nov 9, 2018, 02:31 PM
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If anything its probably overkill but ill check the datasheet when i get a chance.
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Old Nov 9, 2018, 03:00 PM
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That is exactly what I was thinking, but I have one already as a spare for the diode in the original circuit design. I just soldered up VERY short leads and connectors to attach directly to the motor. So if you thinking it is anything other than overkill, please let me know ASAP cause I am going to bolt this sucker onto the fuel pump this weekend. I would rather go for overkill than min-spec and have it burn out over time. That was a great catch, I thought this SSR was immune to flyback.
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Old Nov 10, 2018, 03:14 PM
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Ok I installed the overkill kickback diode!
I also ordered two more for spares since the circuit now uses two of them.



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Old Nov 10, 2018, 05:41 PM
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based on the data sheet the diode should be ok. A 30 amp constant current rating would be better but it has 160amp surge so that will probably make it work out fine. Do you know how many amps you are drawing through the diode in your original application?

https://www.vishay.com/docs/89454/vft2045bp.pdf

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Old Nov 10, 2018, 10:40 PM
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Originally Posted by Biggiesacks View Post
based on the data sheet the diode should be ok. A 30 amp constant current rating would be better but it has 160amp surge so that will probably make it work out fine. Do you know how many amps you are drawing through the diode in your original application?

https://www.vishay.com/docs/89454/vft2045bp.pdf
When the DW350il is being run at low voltage it pulls under 7.7 amps through the dual voltage power supply diode. Deatschwerks was kind enough to test it at 9v for me and provide the current curve at that voltage.

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