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Master_Scythe

Linear voltage boost?

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So maybe I'm thinking about this too 'simply' but since there is a reliable linear way to DROP voltage, is there a reliable linear way to increase it too?

 

 

I have a new Air Fuel ratio controller, with a linear 0-5v output.

Is there a way to boost that 5v to 20v, linearly (so 0 is still zero?)

 

Right now, I'm using a standard voltage gauge and just 'know what voltage is what; each step from 0v = 10:1 - 5v = 20:1

 

 

since I only need enouge current for the digital display to monitor (it has its own 12v V+ source) I'm hoping its possible.

 

 

Failing that, I can fall back to a voltage divider, and use a 'narrowband gauge' (0-1v) with the wideband output (0-5v) but I'd lose a fair bit of reliable resolution.

Edited by Master_Scythe

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Probably use a voltage doubler circuit then reduce voltage from there.

 

Alternatively, sample periodically with ADC then generate what you want from there. But the complexity is probably way more than you'd want to deal with.

 

http://en.wikipedia.org/wiki/Voltage_doubler

 

Might be worth looking at DC to DC converter circuits too.

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I have a new Air Fuel ratio controller, with a linear 0-5v output.

Is there a way to boost that 5v to 20v, linearly (so 0 is still zero?)

 

Yup, look into non-inverting OP amps. You should be able to get the parts from Jaycar for less than $20, and build it yourself with very basic soldering skills.

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It's called an amplifier, and so long as you have it setup right, it will multiply the signal with the gain you require.

Down side is you will need to supply it with a voltage greater than the output range.

 

So to turn a 0-5V analogue output into a 0-20V signal, you will need a supply voltage of say 24V to run the amplifier.

Thankfully, you are driving a meter, nothing with high current load so power requirements won't be an issue. And 4x voltage gain (12dB) is easy for almost any amp circuit.

 

You could muck around with transistors and a bunch of effort to bias it correctly, but probably better as tastywheat said to grab an opamp, and use the application notes, select a few resistors based on the gain you want.

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Thanks guys!

 

after some more thought; I guess I can now see why a PIC of some sort is used to translate the volts to AFR. 0v should be 10AFR..... which is a problem with this idea.

 

Thanks for the info though! its invaluable, something else I didnt know about electronics yet :)

Edited by Master_Scythe

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You could configure the opamp to offset the output by 10V.

Opamps are often used as the basis of analogue computers. Depending on how you configure them, you can get them to add, subtract, etc the two input voltages.

Edited by stadl
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Interesting project - replicate the terrain following computer of the F-111... though I think they went all digital around the late 80s or so.

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Thanks guys!

 

after some more thought; I guess I can now see why a PIC of some sort is used to translate the volts to AFR. 0v should be 10AFR..... which is a problem with this idea.

 

Thanks for the info though! its invaluable, something else I didnt know about electronics yet :)

 

Super easy to offset the voltage using op amps, it only takes an extra resistor and a stable 10V source:

 

DI79Fig05.gif

 

You can read about how to calculate the values for each of the resistors here: http://www.maximintegrated.com/en/app-notes/index.mvp/id/803

 

You can do it with a PIC (I would strongly suggest Arduino if you're not familiar with embedded programming), but I guarantee it's going to be a lot more work, more complicated in terms of the number of components required to get to 10-20V, more expensive, and the output is going to be lower quality because of the necessary ADC and DAC.

Edited by tastywheat

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You could configure the opamp to offset the output by 10V.

Opamps are often used as the basis of analogue computers. Depending on how you configure them, you can get them to add, subtract, etc the two input voltages.

 

Man I've been reading all night trying to learn this, but it seems like the rate is tricky, because on one side I have 5 volts, and the output is '20' numbers (in this case volts, for display).

So that's 2 volts to every 1 measured volt.

 

Damn tricky without a background in this; I'm still reading though.

 

If anyone knows enough without work to tell me exactly how, thats great, otherwise I'll be trying to map some schematics and you can laugh at me :P

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Got datasheets? Often they'll have the simplest case example circuit diagram which will be plenty easier to work out than picking it from a large one.

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If anyone knows enough without work to tell me exactly how, thats great, otherwise I'll be trying to map some schematics and you can laugh at me :P

 

As Rybags pointed out, datasheets or product numbers would help.

 

What's the end goal? Turning a 0-5V signal into 10-20V?

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Correct.

 

I have a wideband sensor\controller, which has a linear output of 0v to 5v, indicating a 10:1 to 20:1 AFR.

 

I've been using a normal $1 digital LCD voltage display from ebay to show the voltage between 0 and 5, and just have a sheet showing me what that would be in AFR (since its linear, thats easy).

 

But I thought, using the same display, it'd be neat if I could show actual AFR.

 

So if I could get 0~5v equaling 10~20V linearly, thats a win!

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Wish i could help i was trained in this type of work in TV servicing made these up on the fly.

 

Damn old age is turning my brains into fudge.

 

Maybe buy a small transformer and put a filtering circuit into a Voltage regulator IC.

 

When i built my first power supply in electronics i built it for testing ,so the voltage was variable from +5v up too 12v+ with low amps. I achieved by using a Pot ( Manual Voltage adjustment ) and put a analogue meter in line to measure it. I suppose i could have built a voltage stepping circuit into if i wanted for the higher voltages.

 

This was for DC only not sure if you want AC ?

 

But if you need these type of circuits in your work for testing items and repair ,it might be best to grab a soldering iron and head to Jaycar or Altronics and grab a Power supply kit and ask if its variable in voltages.

Edited by codecreeper

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Correct.

 

I have a wideband sensor\controller, which has a linear output of 0v to 5v, indicating a 10:1 to 20:1 AFR.

 

I've been using a normal $1 digital LCD voltage display from ebay to show the voltage between 0 and 5, and just have a sheet showing me what that would be in AFR (since its linear, thats easy).

 

But I thought, using the same display, it'd be neat if I could show actual AFR.

 

So if I could get 0~5v equaling 10~20V linearly, thats a win!

 

Ah, got it. I misinterpreted 'standard voltage meter' to be an analog dial or something that you specifically wanted to use, over a cheap LCD display.

 

If you're not attached the display you already have, using an Arduino is probably going to be simpler, and gives you the ability to customise what's sent to the display, add additional sources of information, and/or add forms of user input.

 

You're going to need the following:

 

Arduino nano or mini ($5-13) Example

Breadboard (simple, easy, not quite robust) or veroboard/prototyping PCB (requires soldering, robust) ($2-5)

Display ($3-10) LED Small LCD 1 Small LCD 2 Bigger LCD with keypad (requires bigger arduino) TFT Touch Screen (requires bigger arduino)

Jumper wires and/or solder ($3-5) Example

 

The programming required couldn't be simpler. Start here, read about ADC here, and then how to display the information here (may change depending on display chosen).

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Element 14 is exceptional. Free overnight delivery for most parts, ridiculously large catalogue, and they're building a great Arduino and RPi range these days. It's all high quality stuff though, so it tends to be more expensive than the dodgy Chinese retailers.

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Brain dump incoming:

 

This is a good candidate for an Arduino project, though it can certainly be done with discrete components if that's the road you want to go down.

 

To go the discrete route, you have a few options. Keep your black-box voltmeter, and build an opamp circuit with negative feedback. The limitation of this is that if the opamp's output needs to go 0-20v, then you need a >20v source for the positive rail. Alternatively, you could pump your 0-5v signal into a jellybean ADC, connected to some 74-series logic to drive some 7-segment displays. This eliminates the need for a 20v rail.

 

If you use an Arduino, you have a much higher range of possibilities, with a potentially much lower component count.

 

The chip used on the base model Arduino (the Atmel ATMega328P) contain 10-bit ADCs, and a reasonably stable internal 1.1v voltage reference. The idea would be that you would power the chip through a linear or switchmode regulator, enable the internal AREF in software, then feed your 0-5v signal through a potential divider (scaling the range down to 0-1.1v) into an analogue input. This will give you values between 0-1023 in software, then (x / 1023) * 20 to get your final value.

 

The ATMega328 also has the option to use Vcc as the reference, but this might fluctuate (esp. in an automotive environment) and affect the readout.

 

For output, there are enough digital outputs on the ATMega328 that you could directly drive 7-segment displays from the chip, so it can be as simple as that.

 

You could also display your values as a bar graph, or even a cool-looking charachter LCD display. Using a microcontroller makes all these things doable while keeping a low component count, it's all done in software.

 

Edit: Something like this:

 

mRzLOaP.png

 

- Set the "fuses" to use the internal oscillator

- Not shown is income filter cap

- 7-seg displays are shown as common-anode. If they are common-cathode, connect the common pins to ground instead, and invert digit bitmasks in software.

Edited by SquallStrife
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i cant help with this, because i dont know shit. but i do want to check if i understand your goal.

 

your current reading is x, and you want the display to read 2x +10 -- right?

 

so would it be feasible to add 5V from USB power to the 0-5V output of your controller and then amplify that 2:1?

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Tasty, thats amazing,

and Squall, what an effort! thank you!

 

I've been going through each solution and I guess its time for me to learn some basic arduino.... Ive been looking for an excuse.

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Your other option is to ditch the LCD that displays voltage, and replace it with an LCD that displays current in milliamps.

 

Then you need to translate 0v-5v to 10mA-20mA which is a spectacularly easy thing to do. It will only take 2 resistors if you already have a regulated voltage source (of, say, 10v):

 

R56lqj6.jpg

 

 

This would only really work if it isn't battery operated. 20mA is nothing for a car battery, but an issue if you're powering it off AAs or a random small Li-Ion. If you can get a MICROAMP digital LCD, though, then just multiply the resistor values by 1000 and enjoy the fact it will draw 20 microamps max.

 

Rob.

Edited by robzy
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Your other option is to ditch the LCD that displays voltage, and replace it with an LCD that displays current in milliamps.

 

Then you need to translate 0v-5v to 10mA-20mA which is a spectacularly easy thing to do. It will only take 2 resistors if you already have a regulated voltage source (of, say, 10v):

 

R56lqj6.jpg

 

 

This would only really work if it isn't battery operated. 20mA is nothing for a car battery, but an issue if you're powering it off AAs or a random small Li-Ion. If you can get a MICROAMP digital LCD, though, then just multiply the resistor values by 1000 and enjoy the fact it will draw 20 microamps max.

 

Rob.

 

Now THAT is thinking outside the box, and I love it.

 

Regulated voltage source eh...... ewww. lol. Car voltage is notoriously unastable.

Bass kicks from my subs asside, aircon and standard RPM can change the input voltage by an entire volt.

 

UNLESS you mean my OUTPUT voltage of which I'm monitoring, that IS regulated, 0-5v

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Now THAT is thinking outside the box, and I love it.

 

Regulated voltage source eh...... ewww. lol. Car voltage is notoriously unastable.

Bass kicks from my subs asside, aircon and standard RPM can change the input voltage by an entire volt.

 

UNLESS you mean my OUTPUT voltage of which I'm monitoring, that IS regulated, 0-5v

 

 

All you need for a (relatively) stable 10V source is something like this: http://www.dx.com/p/geeetech-lm2596-dc-power-down-adjustable-supply-module-red-370785#.VTQ6aM6GWS0

 

The above is a switch-mode DC-DC converter that will 'intelligently' convert your dirty supply to a clean 10V, accounting for shifts in voltage due to your stereo, AC, headlights etc. If your bass is still flicking the measurement around, adding larger capacitors should solve the problem.

 

Robzy's solution is pretty damn elegant, but make sure you get a panel meter with the right 20ma range. E.g. http://www.aliexpress.com/item/0-20mA-DC-3-1-2-Digit-LCD-20mA-Ampere-Current-Digital-Panel-Meter-AMP/32282566991.html

 

Also, using a precision linear potentiometer (variable resistor) for the 500Ω component will allow you to adjust the range. This is generally a good idea, as different tolerances within the system will typically result in a certain level or error for the output. The potentiometer on the power supply will allow you to adjust the offset.

Edited by tastywheat

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Wow, now I'm torn.

 

That's super simple, and I know tens, if not hundreds of car guys spending an additional $200 on JUST the 'gauge section' of their meters, who would love a 2~3 component 'solution'.

 

On the flip side, using an Arduino, I get the chance to learn how to program one, DIY something myself, and (compared to $200), come out not much more expensive than Robzy's solution.

 

I have some DC-DC converters at home (about 10 left in my project box I think...) so maybe I'll try both. But Arduino first :)

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