Have 5.19V DC and want 5.00V DC .... please

[Mikel_NY]

hey All,
i have an old wall charger that is 120v AC input, 5V DC output @1 amp. when i put meter on output i get 5.19v dc. i need 5.00v dc.

How can i get to 5.00v?

I'm making a throttle position sensor test tool. manual is asking for 5.0v +,- 0.01

i plug power into wall, plug in TPS, use meter to probe common negative to supply 5.0v to confirm start setting then probe TPS out to negative and set TPS to 4.0 or 4.20.

thank you in advance for any help

 

[berkeman]

hey All,
i have an old wall charger that is 120v AC input, 5V DC output @1 amp. when i put meter on output i get 5.19v dc. i need 5.00v dc.

How can i get to 5.00v?

I'm making a throttle position sensor test tool. manual is asking for 5.0v +,- 0.01

i plug power into wall, plug in TPS, use meter to probe common negative to supply 5.0v to confirm start setting then probe TPS out to negative and set TPS to 4.0 or 4.20.

thank you in advance for any help

Just use it as is. You should be fine.

 

[oz93666]

You are probably at the limits of your meters accuracy ... put two or three meters across the supply and you'll be surprised at the variation in readings ..

Also this is the voltage at no load you are reading .. it will drop once current is drawn ... also probably as mains voltage fluctuates this will effect voltage ...

If you're really sure you need such an accurate supply you can find many cheap voltage regulators on ebay you can adjust the voltage yourself , but you will need to feed it 7v or more ... make sure to buy a few meters and take the average of the readings to get an accurate output ...

I find it hard to believe you need such a precise supply ... Is there no way of trying the supply you have and seeing if it works ?

 

[f95toli]

I would suggest looking for 5.0V voltage references instead of a regulator; most sensors want an accurate voltage but won't draw much current (1% 5V refrences are dirt cheap).
But yes, you will probably need a 7.0V or so supply,

 

[sophiecentaur]

You have to ask what is 'special' about the 5V requirement? If it's required as a supply for some circuit then, unless the circuit is really poorly designed, it should be more than capable of dealing with power supply variations. (Read the detailed spec).
If you need 5V as a reference then a wall wart is not the way to do it.

 

[Mikel_NY]

I need 5.0 v as a reference. I don't see the need for any current. Once I have the 5.0 reference then I move pos probe to tps output to read a value. Then lock the tps down.

If the tps is at true 3.9 v the snowmobile will bog off idle and accelerate sluggish.
If the tps is set at true 4.3v then detonation sets in and you rebuild the motor.

The sweet spot is @4.25-4.28 BUT I need a perfect 5.0 input or the output is skewed.
Could I "assume" that if I input 0.2 over value the I could adjust output by same to reach the "difference" in voltage that the book is calling for?

 

[sophiecentaur]

Have I missed something here? If the system you are developing is to work on a snowmobile then shouldn't you be deriving all your circuit power (references too) from the 6 or 12V battery?

 

[Averagesupernova]

Have I missed something here? If the system you are developing is to work on a snowmobile then shouldn't you be deriving all your circuit power (references too) from the 6 or 12V battery?

Automotive sensors typically use a 5 volt supply from the computer.

 

[Mikel_NY]

The tps needs to be set to tell the CDI where the throttle plates are in relation to rpm so the CDI can trigger spark at correct moment. This is all happening at 8000+ events per minute!

A slight clocking (degree) of the tps makes a huge difference.

I'm making a tool to set the clocking of the tps when sled is NOT running.

 

[sophiecentaur]

Automotive sensors typically use a 5 volt supply from the computer.

That makes sense. So, clearly the sensor needs the '5V' from the on board computer. That will clearly be appropriate for the system as it's designed that way.

 

[Mikel_NY]

I need to supply the 5.0v there is no on board supply to use when setting the TPS hence the reason I'm here asking if there is a way to reduce my 5.19v "wall wart" to supply 5.0v when setting the TPS?

How can I get a 5.00v DC output from a wall plug vs using a 9 volt battery? (They are always low or dead when needed) I would only be in garage and never out and about so 120v AC will be avalible.

 

[sophiecentaur]

I need to supply the 5.0v there is no on board supply to use when setting the TPS hence the reason I'm here asking if there is a way to reduce my 5.19v "wall wart" to supply 5.0v when setting the TPS?

How can I get a 5.00v DC output from a wall plug vs using a 9 volt battery? (They are always low or dead when needed) I would only be in garage and never out and about so 120v AC will be avalible.

I still don't understand where the TPS gets its supply from and why you can't use the same source. Alternatively, get hold of a higher voltage wall plug (9 or 12V) and use a 5V regulator. People are always throwing out these things. Ask around. Alternatively, get hold of a rechargeable battery and a charger (also available all over the place). You have a problem if you want this all to be done for free but you're already spending some money. Perhaps you just need to come to terms with spending on something you thought you could get for free.

 

[NascentOxygen]

when i put meter on output i get 5.19v dc. i need 5.00v dc.

How can i get to 5.00v

Probably if you connect a resistor across it the 5.19V will drop a little. Try 47kΩ, or 33kΩ, or 22kΩ, or some resistance that's higher or lower, and watch your meter. But as others are indicating, no sooner will you have got it right then the fridge or something will cut in and your 120V drops a bit and takes all the unregulated wall warts with it.

It seems you are needing it to be 5.00V only for a few seconds, so this might work out if you're patient.

 

[Mikel_NY]

I don't mind spending some money. I'm over my head with circuits. I have wall plugs with 9v DC out. I will buy a 5v regulator.

Could someone post a simple circuit for me to wire this together? Will there be other parts needed?

 

[CWatters]

I'm making a throttle position sensor test tool. manual is asking for 5.0v +,- 0.01

That's an accuracy of 0.2%. It will be very hard to find or make a 5V supply that accurate. Things like temperature changes might effect the voltage more than that.

How accurate is the multi meter you will use to check the voltage? Some multi meters are less accurate than the number of digits they display might suggest. Typical handheld meters can be accurate to about 0.5% (say +/- 0.025V at 5V). Bench meters can be better at around 0.01%(+/-0.0005V).

I suggest you post data on the throttle position sensor and info on what would constitute a pass/fail on test.

 

[CWatters]

PS I suspect the data for the TPS only says +/-0.01V to ensure they can claim it's output is accurate to some specific % without a built in regulator. In practice most systems won't need the output of the TPS to be as accurate as claimed in the specification so a lower accuracy power supply is acceptable.

 

[Rive]

I'm making a throttle position sensor test tool. manual is asking for 5.0v +,- 0.01

That kind of accuracy is voltage reference range, not supply range. It'll be hard to do this as 'supply', and I think it would require some kind of 4w feedback from the sensor.

As reference, it can be done with some kind of boost DC-DC converter (bring up the voltage to ~7V), lot of filtering (DC-DC makes a lot of noise) and a 5V reference.

But: I don't think that you really need that accuracy. I think it would be enough if that source you have can supply a stable voltage.

 

[AlexCaledin]

A simple Voltage Inverter can make 5.0 V DC no matter whether the input voltage is more or less:

 

[Rive]

Step-up converter chips can be used.

If that accuracy is really needed, then you don't wanna' do this with direct DC-DC, nor you wanna' mess up the grounding just like that...

 

[AlexCaledin]

As for the ground, we can modify it like this (the switches are simultaneous),

― physically, it's a simple "buck" regulator with an n-channel MOSFET and a diode added.

 

[Mikel_NY]

the tps does not use any current ... if i read the wall plug directly its 5.19v dc. i have read this for a few days w/ no variation. once i plug in the tps, the wall wart is still 5.19v. then i move pos prob to tps out just to read its value.

i don't know the difference of a supply vs a reference voltage like some keep referring to. I'm a rookie in electronics but learn quickly the basic stuff. i made a black box in this video ... i want to change the 9v battery out and add wall plug. i will dig up schamdic for the black box as i threw mine out (frustrated w/ batt)
the pic is a newer style of the black box. i would guess the lump in the upper right is a 5v regulator.

 

[Rive]

. i want to change the 9v battery out and add wall plug.

Don't.

If it's any precision stuff then it'll perform way better with battery than with any wall plug.

We made some similar circuit for calibration/testing, and the filtering was a nightmare. At the end we reverted to battery and gained two decade in accuracy just by that.

 

[sophiecentaur]

PS I suspect the data for the TPS only says +/-0.01V to ensure they can claim it's output is accurate to some specific % without a built in regulator. In practice most systems won't need the output of the TPS to be as accurate as claimed in the specification so a lower accuracy power supply is acceptable.

That's a serious point. I cannot imagine that a system that's to be installed in a vehicle could ever require such accuracy in supply volts or a reference voltage. There would always be feedback in such a system to make it fault tolerant or it would only run for five minutes on a good day. I think we and the OP are not approaching the problem in the best way. If it won't apparently work with the cheap and cheerful 5V then there is probably another problem involved - perhaps the basic testing method should be different. Where does the sensor get its reference from when it's on the vehicle? If the timing is dynamically controlled then the engine needs to be running during a test; the static offset won't be relevant and will probably be taken care of by the engine control system.

 

[sophiecentaur]

I just looked at the video again. If the factory setup is around 5% wrong then how can it be a critical factor, in any case.
I also note that they use a battery. They really are a very good way of providing a reliable source of volts and I would not imagine this work would need to be done very often of a snowmobile.

 

[jim hardy]

Could someone post a simple circuit for me to wire this together? Will there be other parts needed?

I don't believe your TPS draws zero current.
Every one i encountered was an adjustable resistor (potentiometer) of a few thousand ohms. So i think it'll draw a goodly chunk of a milliamp.

This gizmo is called a "shunt reference" , it absorbs current trying to maintain 5.000 volts cross itself. Sort of a super accurate zener diode. You buy whatever accuracy you want, from about +/- 2 to 20 millivolts.

Datasheet here, http://cds.linear.com/docs/en/datasheet/1634ff.pdf
just one of many places to buy them
http://www.digikey.com/product-detail/en/linear-technology/LT1634CCZ-5-PBF/LT1634CCZ-5-PBF-ND/961484

It should work so long as your TPS draws less than about 1.8 milliamps.
Use it only with that 5.2 volt supply you have. It'll burn itself up trying to hold down a 9 or 12 volt supply.

http://www.digikey.com/product-detail/en/linear-technology/LT1634CCZ-5-PBF/LT1634CCZ-5-PBF-ND/961484

There's plenty of folks here who can show you how to improve on it so you could use it with the snowmobille's 12 volt battery .
Your friends will all want one of those...buy extra parts.

[ mod note: spelling corrected ]

Thanks moderator - guess i didnt proofread it close enough.