5 Vref

http://jbperf.com/io_extender/index.html
http://jbperf.com/io_extender/tinyIOx.html for the TinyIOx

5 Vref

Postby Yves » Tue Feb 13, 2018 3:59 am

I learned that MS has a current limit on the 5 Vref. Can you make an additional 5 Vref circuit to supply the 5V to additional sensors ? Any problems with incompatibility when you do this ?
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Re: 5 Vref

Postby dontz125 » Tue Feb 13, 2018 1:43 pm

Do you mean the MegaSquirt or the MicroSquirt? The big MS has a voltage regulator rated to 500mA and some pretty serious heat sinking. The uS has a regulator rated for a full amp, but has almost nothing in the way of a heat sink; B&G have recommended that no more than 25mA be used for VRef.

If you need to use an external power supply to add a few extra buckets of 5v milliamps to a uS or uSM, there are two ways to do it. You can use a following regulator that self-matches the output at the VRef header pin (and I *cannot* find an example of this online), or you could remove L1, and wire your regulator output to the L1 pad closest to the board edge. This allows the secondary regulator output to be read by the VDDA pin on the processor, to keep your sensor reading accurate. Don't just try to run it through the VRef pin on the header, though; the slight resistance - the *changing* resistance - of the polyfuse will confuse the VRef reading at the chip.

If you really are talking about an aluminum-boxed MS, you can do the same trick as with the uS, just remove L2 instead. With the bigger MS, there is also the option to simply uprate the regulator; there are 5v TO220 LDO regulators that go as high as 5 amps! If you go this route, you'll probably need to uprate both polyfuses, or else they'll simply block all your shiny new current.
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Re: 5 Vref

Postby Yves » Tue Feb 13, 2018 3:07 pm

Ok, this is not as simple as I hoped apparently.

I use a V3.57 board, so it's a no-go as far as taking off parts and mounting others.

Any ideas what stuff like a hall sensor, map, iat, clt, iox etc use in terms of current ? My guess is that with everything I'm currently running I might be close to .5 A
25 mA looks like a very low number, considering that the on board map alone uses something like 7 mA.
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Re: 5 Vref

Postby dontz125 » Tue Feb 13, 2018 4:04 pm

The V3.57 uses the same through-hole style voltage regulator as the V3.0; it's the left-most TO220 on the heat sink bar, beside the DB9. L2 is just above the boot header, and comes away easily with a soldering iron, some fresh solder and lots of flux.

The IOx processor is the big eater in your list, and I would say around 75-100mA, but the IOx has its own power supply. The rest ... I'd be astonished if it added up to 50mA. The normal sensors are 2-5mA, the MAP /Baro is 7-10mA. The Hall sensor depends on the model, but again, it shouldn't be more than a handful; the Littelfuse 55505 is rated for 20mA max. You should be nowhere *near* the 500mA limits of a V3.57 board. I don't know what the consumption is of the MS3 card itself, but the MS2 chip was IIRC close to the 100mA of the IOx.

Just to clarify - 25mA is the VRef limit of a MICROSQUIRT, which doesn't have an on-board MAP sensor. Most of the power it consumes goes to operating the controller itself, and doesn't have the heat rejection capability to process more current.
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Re: 5 Vref

Postby Yves » Tue Feb 13, 2018 4:38 pm

To clarify I'm currently reworking my manifold and was planning on adding 8 map sensors (one for each runner) with the goal of easily balancing individual cyls and seeing what goes on when driving in terms of pulsations in the runners

8 map sensors would total 8 X 7 mA = .056 A

Currently I run the following :
Iox
iat
clt
2 X maf (frequency)
8 WB ego's
crank hall sensor
cam hall sensor
wheel hall sensor
tps
coolant pressure sensor
fuel pressure sensor
fuel pump speed regulator
Oil pressure sensor
Oil temp sensor
acceleration sensor
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Re: 5 Vref

Postby dontz125 » Tue Feb 13, 2018 4:53 pm

The WBO2 sensors are going to be hogs, but aren't they and their controllers 12v? If these are 14point7 SLCs, they're either self-powered, or you've got so many they should be in a box with their own power supply! Same with the IOx; it should have its own on-board regulator.

The hall sensors will probably be 10-20mA each, the temperature sensors should be 1-2mA each, and the TPS 5mA. I have no clue what the pressure sensors draw; that's something to check no the data sheet.
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Re: 5 Vref

Postby Yves » Tue Feb 13, 2018 5:19 pm

The WB's do have their own ps. They're 14point7 Unless mistaken the iox doesn't have an on board 5V regulator.

And Don the pressure sensors came from you remember...
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Re: 5 Vref

Postby jbelanger » Tue Feb 13, 2018 5:26 pm

I think you have the full size I/O Extender and not the TinyIOx.

As Don says, the IOx has its own power supply. I also assume you've got some of those sensors connected to the IOx ADC inputs so you should be using the Vref (and ground return) from the IOx to power them. The IOx has the same type of voltage regulator as the Microsquirt but it has more heat sink capacity so I would not worry about adding 100mA of current from sensors.

I should also add that the IOx has been designed with the possibility of using an addition power supply for Vref. If that's something you want to consider, it is simply a question of removing a solder jumper and connecting the additional power supply to the correct pin on JP5.

Jean
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Re: 5 Vref

Postby Yves » Tue Feb 13, 2018 6:20 pm

jbelanger wrote:I think you have the full size I/O Extender and not the TinyIOx.

As Don says, the IOx has its own power supply. I also assume you've got some of those sensors connected to the IOx ADC inputs so you should be using the Vref (and ground return) from the IOx to power them. The IOx has the same type of voltage regulator as the Microsquirt but it has more heat sink capacity so I would not worry about adding 100mA of current from sensors.

I should also add that the IOx has been designed with the possibility of using an addition power supply for Vref. If that's something you want to consider, it is simply a question of removing a solder jumper and connecting the additional power supply to the correct pin on JP5.

Jean


Yes, I have the full size IOX. So if I'm right, I can put the additional maps on the spare adc's without worry.
I assume pin 3 is the one to use on the DB37 for power to the map sensors ?
Can I assume I can use the standard conditioning circuits as per your website explanation ?
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Re: 5 Vref

Postby jbelanger » Tue Feb 13, 2018 6:31 pm

Correct on all points.

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