DFH - Defacto FreeEMS Hardware in KICAD

Jared's unmaintained and never-used TA based "Defacto FreeEMS Hardware" design.
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nitrousnrg
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Re: freeEMS_1.0 rev A KICAD

Post by nitrousnrg »

Take a look to the LM2931 as a replacement for the 7805. Also, LM2936 is slightly better when output current don't exceed 50mA (for example: 2 pressure sensors + temperature sensors + conditioning circuits)
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jharvey
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Re: freeEMS_1.0 rev A KICAD

Post by jharvey »

I just checked and you are correct, the BOM calls for newark 45J1442 which is a 7805. A LDO certainly won't hurt it, it might cause the cost to go up a pinch, but not much. Do you have a recommended vendor or mfg #? For example like the newark number posted above. I see the LM2931 is also sold as a comparitor, and the LDO's have several other digits for specific options.
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nitrousnrg
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Re: freeEMS_1.0 rev A KICAD

Post by nitrousnrg »

My chooses are restricted to what digikey have. That is my only filter.

Specifically, the one I'd use is LM2931AT-5.0NS-ND (http://search.digikey.com/scripts/DkSea ... T-5.0NS-ND)

I'm considering to develop a board from scratch (I started it using your schematics, but I'm just not sure if i will finish it). As always, my plan is to get all the components in a single order from a single vendor, since at least 30% of the cost is in the shipment to Argentina.
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Re: freeEMS_1.0 rev A KICAD

Post by jharvey »

Awesome and glad to hear you can use it. If you have any questions feel free to ask. I know a couple things that could be improved upon. Are there any specific goals for your version?
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Re: freeEMS_1.0 rev A KICAD

Post by nitrousnrg »

Which things could be improved?

My version is ment for Argentina, where I don't expect the final user would buy the parts by itself and start soldering everything down. I'd sell it ready to run.
First of all, it'll have P&H, since my uncle bought a Fiat Uno Turbo i.e., and it have low Z injectors.
Second, it won't have Fred's board, cause I won't pay 150 U.S. dollars for it. The cpu is embedded onboard, with a FT232 (USB is a must these days), and expects a connector board.
Third, if I can stand the development, It will be my career's final project. I've talked to my professors and my career director, and they were pretty happy with this.
I'm removing the things I consider I won't use, and adding some others that I will (external MAP, exhaust temp, oil temp, and a few extra inputs).
I should make a new thread for it, but I don't want to leave an orphan thread/project here. My design is in github, as a branch of yours anyway.

Back to the topic, I'm using 2 power supplies but not like you do. One of mine is for digital stuff (micro, rs232, usb , lm1815), the other is only used to power up the pressure sensors, thermocouples, and to be the analog reference (this one is smaller, and with tighter tolerances). I find this approach better than a regulator for the micro and another regulator for other things.
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Re: freeEMS_1.0 rev A KICAD

Post by jharvey »

nitrousnrg wrote:Which things could be improved?
Mostly things that are also posted in 5554, and there may be some debate about if they are improvements. I'll draft the pro's and cons here.

In 1.0 it uses 1ch ign/inj drive which is very flexible and allows for some interesting performance variations as well as it offer multiple vendors to provide parts. It also uses the LM1815 which uses a common ground with other grounds, but increases common mode rejection and decreases skipped tooth warping. It doesn't require software to configure it, so it's easier to develop with. Also also, 1.0 is a 2 layer design, which allows you to see and scope the traces so you can find and identify problems like a noisy ground.

In 5554 it uses 4 channel ign/inj driver which is easier to asm and offers more feed back then the above noted 1 channel. However it's harder to develop against because it requires a data bus for configuration and feed back, also it's the only chip that will work with it's PCB pads and has less performance options. This one uses the MAX9926/ect which doesn't use a common ground on the signal wire and has a much higher common mode rejection, as well as it eliminates the skipped tooth warping. However, it typically desires additional MCU support, which makes it harder to develop with. This is a 4 layer board which allows more flexibility in the ground and power planes, but then they are harder to probe and measure with a scope, so obscure situations can be harder to diagnose. However, it would likely have a lower noise floor on the average install, so those obscure issues should be minimized, assuming the board is drawn correctly that is. MS is a 4 layer design.

I think there may have been a couple others listed in my todo list as well.

So both designs have pros and cons. So depending on the expected audience, they could be improvements, or limitations.
nitrousnrg wrote:My version is ment for Argentina, where I don't expect the final user would buy the parts by itself and start soldering everything down. I'd sell it ready to run.
Cool.
nitrousnrg wrote:First of all, it'll have P&H, since my uncle bought a Fiat Uno Turbo i.e., and it have low Z injectors.
For low Z, I'd recommend jperf's (sp) high Z to low Z drive board. Or near equivalent. That will allow the feature and expense to be added or removed based on the application.
nitrousnrg wrote:Second, it won't have Fred's board, cause I won't pay 150 U.S. dollars for it. The cpu is embedded onboard, with a FT232 (USB is a must these days), and expects a connector board.
I here you there, the board does seem a bit pricey, and it's good for prototyping, but not good for assembly. I'll be interested in your schematic symbols and modules (foot prints). I'd like to see them available in KICAD land.
nitrousnrg wrote:My design is in github, as a branch of yours anyway.
I'll have to go check it out. Sounds interesting.
nitrousnrg wrote:Back to the topic, I'm using 2 power supplies but not like you do. One of mine is for digital stuff (micro, rs232, usb , lm1815), the other is only used to power up the pressure sensors, thermocouples, and to be the analog reference (this one is smaller, and with tighter tolerances). I find this approach better than a regulator for the micro and another regulator for other things.
5554 uses what I consider a better power supply, it uses a switching device that is more efficient / less heat than a linear regulator.

Well it's off to the bump and grind.
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Re: freeEMS_1.0 rev A KICAD

Post by Fred »

nitrousnrg wrote:Back to the topic, I'm using 2 power supplies but not like you do. One of mine is for digital stuff (micro, rs232, usb , lm1815), the other is only used to power up the pressure sensors, thermocouples, and to be the analog reference (this one is smaller, and with tighter tolerances). I find this approach better than a regulator for the micro and another regulator for other things.
Ummmm, is that NOT what we have? (more or less)

The only trouble with that is that the reference voltage must be within a small tolerance of the micro supply or you'll damage the device. If you can ensure the two never deviate much, great, otherwise, keep the reference internal to the micro, keep the micro supply solid, and use the second only for external sensor references which are susceptible to shorting etc.

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nitrousnrg
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Re: freeEMS_1.0 rev A KICAD

Post by nitrousnrg »

Ummmm, is that NOT what we have? (more or less)
Nope, you don't have a regulator dedicated only to analog things. In yours, both of them have digital stuff that puts noise in the power line.

Jared, everything is available. I've created the microncotroller component (schematic), the ftdi was something I've made a while ago, and created the SMD diode . module (SOD 123).

The P&H driver is based on jperf's circuit. I put 6 drivers, its a shame that it don't come in SMD version.
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Re: freeEMS_1.0 rev A KICAD

Post by MotoFab »

Fred wrote:The only trouble with that is that the reference voltage must be within a small tolerance of the micro supply or you'll damage the device. If you can ensure the two never deviate much, great, otherwise, keep the reference internal to the micro, keep the micro supply solid, and use the second only for external sensor references which are susceptible to shorting etc.
There are reasons to use a different reference voltage for the ADC. And for using the analog supply as the reference. Does the datasheet say that a different reference voltage will cause damage?
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Re: freeEMS_1.0 rev A KICAD

Post by jharvey »

nitrousnrg wrote:Jared, everything is available.
Hey, look at that you have a branch. I see it now.
nitrousnrg wrote:The P&H driver is based on jperf's circuit.
I forget if that can handle a high and low impedance injector. Can it do both? I like the SMT, looks much more packed together and cleaner. I'm curious how you plan to assemble them, do you have a reflow oven?

Perhaps this should migrate to it's own thread.
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