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Old 01-28-2018, 09:04 PM
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Default How to connect/install an AMP VOLT METER

An Amp Volt Meter is a small, dual read out digital meter

...that will show the voltage of your battery pack (top reading, in red)

...& it will also show the amperage (Amps) that your motor is drawing from the battery pack (bottom reading, in blue)

This is the one I have/used

https://www.ebay.com/itm/291152585319

...it was only ~$15.00 delivered

...it's 48 x 29 x 21 mm (~2" x ~1 1/8" x ~7/8")

...& it comes with a (500A/75mV) "Shunt"
(basically a giant resistor) that sends information to the meter


IMHO It's simple to install & very easy to hook up


It only has (5) wires to connect

The small plug has (2) wires
(they supply the power to the meter)

...the positive (+) red

...& negative (-) black


The bigger plug has (3) wires
(they are the meters sensor "or data" wires)

...the B+ (red) sensor wire goes to the battery packs positive (+) terminal

...the B- (black) sensor wire goes to the (B-) on the shunt

...the P- (yellow) sensor wire goes to the (P-) on the shunt


* The meter can monitor up to 300VDC (the red (3-plug) sensor wire)

...but it can only be powered by ~5V thru 30VDC (the red (2-plug) power wire)


To begin with,I drew a simple wiring diagram

...to show how I connected the meter to a small 24V 12AH battery pack


I added a switch to be able to turn the meter off when not in use

I also show many of the other components involved

...to help illustrate & show how everything is connected & interconnected


** Since this battery pack is under 30V

...the meter can be powered (directly) by the monitored pack voltage

...but, remember this diagram is ONLY for a 24V system


*** Don't worry, we will cover larger voltage applications - shortly

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  #2  
Old 01-29-2018, 06:45 AM
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Is the amp meter very fast for the initial full throttle from a stop? As in how high of Amp numbers have you seen it show?
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Old 01-29-2018, 08:21 AM
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How many ohms is that shunt?
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Old 01-29-2018, 03:26 PM
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Quote:
Originally Posted by TT540 View Post
Is the amp meter very fast for the initial full throttle from a stop? As in how high of Amp numbers have you seen it show?
Yup! pretty much instantaneous

During the El Turbo tests I did last summer

...the highest I saw the meter reach was 103 Amps

...during the third "Turbo Blast" in this run

...check it out

  #5  
Old 01-29-2018, 05:32 PM
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Quote:
Originally Posted by tinamcjittles View Post
How many ohms is that shunt?
It's listed @ 500A/75mV

I am not really sure, the specs don't specify

I'll check, for ya


OK, Here's what I found on the web


* 500A 0,5% Nominal resistance 150 mkOhm 75mV Voltage drop


How a shunt works

A shunt is necessary in order to measure amps. A shunt is an accurate, very low resistance resistor which is placed "in line" with the wire carrying the current to be measured. It is usually placed in the negative wire from the battery bank, such that all the current going into the battery (charging) or out (discharging) must pass through it.(It also could be placed in series with the negative wire coming from a solar array--or other charging source--in which case it would measure only the solar array current, if that were desired) The shunt needs to be placed near the batteries; since these wires carry very high currents the wires from the batteries must be kept short to minimize electrical losses.

Shunt resistance

When current flows through the shunt, a small voltage is developed across the shunt which is proportional to the current flow. A amp volt meter accurately measures this very low voltage and converts it to the "amps" reading on the meter. The resistance, which is the ratio between the voltage across the shunt and the current flowing through it, is a constant for any particular shunt--and is one of its important parameters. For most substances, resistance is usually described in "ohms", however for some reason shunts are described by the voltage drop that occurs with a certain current: for example: "50 millivolts at 500 amperes." However the meter only cares about the ratio-which is the resistance--so a 500Amp/50 millivolt shunt is equivalent to a 250Amp/25 millivolt shunt. They both have a resistance of 0.1 milliohm, or one ten thousandth of an ohm.

Last edited by Functional Artist; 01-29-2018 at 08:54 PM. Reason: add info
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Old 01-30-2018, 08:24 AM
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Before we wire up the meter

...we need to mount it, somewhere


It could be easily mounted

...in/on a box

...on the steering wheel

...or on the dash board


For demonstration purposes, I'll just mount into a small dash board

...like for a go kart, golf cart etc.


Rounded up some plastic (from the back off an old TV)

I figured ~4" x 8" should work

...measured ~8" & marked it

...used a square to "square it up" & as a straight edge, for scoring

...scored it several times in each direction

...lined it up with the edge of the bench top

...& snapped 'er off nice n clean

then,

...measured ~4" & marked it, scored & snapped 'er off too


Evenly, arranged the meter & a couple of switches

...drew out some guide lines with pencil

...marked just inside but, around the perimeter of the meter hole

...& marked the center of each switch hole

...drilled small holes (~1/8") then bigger (~1/4") holes
(to remove as much unwanted material as possible)

...use a razor knife to "connect the dots"

...& then, a lot of whittling
(slowly removing material right up to the line)

...checking several times along the way for "component fitness"

Yup!, that should do it

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  #7  
Old 01-30-2018, 02:10 PM
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Good information. Thanks for doing this.
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Old 01-30-2018, 06:02 PM
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It's a shame vehicles do not have amp meters anymore (if they ever did) to show how much power they are drawing off the system. These would be nice for those who run lights and other stuff on their karts and buggies.

How much different would the hook up he for an analog gauge for voltage and amps? I'm kind of a sucker for analog type gauges vs digital.
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Old 01-30-2018, 07:35 PM
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Quote:
Originally Posted by Kartorbust View Post
It's a shame vehicles do not have amp meters anymore (if they ever did) to show how much power they are drawing off the system. These would be nice for those who run lights and other stuff on their karts and buggies.

How much different would the hook up he for an analog gauge for voltage and amps? I'm kind of a sucker for analog type gauges vs digital.

Yup!, This amp volt meter could also/easily be used to monitor the battery/electrical system in a gas powered vehicle


Digital or Analog, the connections should be the same


* I have no experience with analog gauges (on karts) but,

I have heard, the digital monitor gives consistently accurate readings

...where an analog gauge is usually only accurate, while sitting still

...when moving, especially off-road, the needle tends to jump erratically
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Old 01-30-2018, 07:37 PM
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Quote:
Originally Posted by Kartorbust View Post
It's a shame vehicles do not have amp meters anymore (if they ever did) to show how much power they are drawing off the system. These would be nice for those who run lights and other stuff on their karts and buggies.

How much different would the hook up he for an analog gauge for voltage and amps? I'm kind of a sucker for analog type gauges vs digital.

Amp gauges bounce with an alternator, hence why they use volt meters now. Amp meters only played nice with a generator.
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Old 01-30-2018, 08:25 PM
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Now, we have the face of the dash done

...lets make a back & top & a bottom

...to help protect the components, connections & wiring


I also, mounted the dash board to a "mock" steering support hoop

...to show how it would/could be mounted on a kart


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Old 01-30-2018, 10:32 PM
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Awesome work FA!!!! I like all the housings and dashboards that you make. It makes everything look so clean
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  #13  
Old 01-31-2018, 09:05 AM
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Quote:
Originally Posted by landuse View Post
Awesome work FA!!!! I like all the housings and dashboards that you make. It makes everything look so clean
Thanks, I always appreciate it when the craftsmanship is noticed
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Old 02-01-2018, 07:43 AM
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Let's get 'er wired up

Rounded up some 22-4 wire (22g.- with 4 wires in one outer jacket)

...looks to be about the same size as the sensor wires used for the meter

I have a big role of it left over from when I wired the alarm system in my garage & I also used it for the wiring harnesses on El Dingo & El Moto too


Looking at the diagram

Start off at the meter

...the big plug has (3) "sensor" wires

...yellow (P-)

...red (B+)

...& black (B-)


The 22-4 wire has red, black, white & green

so, we'll use

...white for yellow

...red for red

...black for black

...& the green is just, left over


The small plug has (2) "power up" wires

...red (+) is the power input for the meter

...& the black (-) is the negative for the meter


* For this application (24V) we can draw the power right off of the battery pack (because it's between the 5V & 30V)

...so, the small plug, red (+) "power" wire can be connected together with the big plug, red (B+) "sensor" wire

...& the small plug, black is unused

I put a ring terminal on

...the yellow wire

...the white wire

...& on each of the black wires

Then, I attached the yellow & the white wires together, with a screw, to the wall if the enclosure divider

...& the (2) black wires together with a separate screw


I ran the "power up" wire thru the switch (with spade connectors)

...to be able to turn the meter off when not in use

** I made all connections, with crimp ends, to show that the meter could be easily hooked up without soldering

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Last edited by Functional Artist; 02-01-2018 at 07:47 AM. Reason: add video
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Old 02-03-2018, 08:29 AM
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Now lets build a mobile amp/volt meter

This way, the meter doesn't have to be

...mounted into the dash

...or hard wired

...can be used on several different karts

...& can be used on/with higher voltage systems (over 30V)


First, you need a box to mount everything into

I didn't have a small plastic box available so, I made one

I rounded up some stuff

... a really old smoke detector

...a broken aquarium air pump

...a circuit tester (blown bulb)

...& some wire


Opened up the smoke detector

...& removed the connector & wire leads, for the 9V battery


Opened up the air pump

...needed the top half of the case for the meter box

...& the bottom half to mount the shunt into


Unscrewed the wire lead from the test light/circuit tester


Drilled a 5/8" hole in one end of the aquarium case

...had to "waller" it out a bit (move drill around while drilling)

...needed a little bigger than 5/8"

...while it was still warm (& kinda soft), I threaded the end of the circuit tester lead into the hole


Then, drilled a 3/16" hole in the same end for the other wire leads



Now, we need a front panel

So, I layed out, marked & cut a panel

out of a piece of plastic from the old TV back

A little roundin'-n-shapin' & 4 mountin' holes


Now, we gotta cut out a spot for the meter

...& since this is (self-contained) battery operated (not switched on/off with the kart)

...we should add a switch (so, we can turn it off when not in use)

so, gotta cut out a hole for a switch too
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  #16  
Old 02-03-2018, 12:45 PM
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Let's get 'er wired up

Remember, the meter has (5) wires

...(2) go to the "power plug" which supplies the power (5V to 30V) to operate the meter

...& (3) go to the "sensor plug" which supplies the data to the meter


I figured a little 9V battery, with it's clip on power leads, would be the simplest/easiest to mount & hook up

So, inside the box, I mounted a 9V battery with a small piece of velcro

...then, I soldered the 9V battery's red (+) wire & the "power plug" red (+) wires together

...& soldered the 9V battery's black (-) lead wire to one terminal of the switch

...& also, soldered the "power plugs" black (-) wire, to the other terminal of the switch, to complete the "power up" circuit


Keep in mind

...the meter needs to be seen "up front" by the driver

...but, the sensor data comes from "in the back" at the battery pack

I figured, ~3' should be plenty

...so, I used ~36" of 22-4/cable to connect the "sensor plug" from the driver compartment to the battery pack

...the yellow (P-) "sensor" wire is soldered to the white 22-4/cable

...the black (B-) "sensor" wire is soldered to the black 22-4/cable


The red (B+) "sensor" wire is soldered to the wire lead from the test light/circuit tester


Back at the battery pack

The shunt is to be connected "inline" with the battery pack's negative cable (-)

...the (B-) (battery -) side of the shunt, is connected to the negative terminal of the battery pack (or as close to it as possible)

...the (P-) (power -) side of the shunt is to be connected to the negative (-) battery cable (the (-) cable going away from the battery)


The black wire (B-) from the 22-4/cable goes to the battery side of the shunt (B-)

...the white wire (P-) from the 22-4/cable goes to the motor side of the shunt (P-)


The wire lead from the test light/circuit tester (red (B+) wire coming from the "sensor plug")
can be easily attached to the positive (+) terminal of the battery pack (or motor's positive terminal)


* I mounted the shunt into the other half of the old air pump box with a couple of zip ties
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  #17  
Old 06-11-2018, 12:29 PM
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I rigged up & tested a "simple" voltage divider to see if I could "safely" & "reliably" power one of these amp/volt meters off of a 48V battery pack. These meters can handle a power supply from 5V thru ~30V.

I used a 3.000 Ohm 1W resistor (R1) & a 1,000 Ohm 1W resistor (R2)

While testing, I noticed that the 3,000 Ohm resistor got kinda warm/hot
...but, the 1,000 Ohm resistor didn't seem to

May need to use a larger wattage resistor

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Old 06-11-2018, 11:55 PM
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Still going strong. Sorry that I don't have any constructive comments, but I am just not a electric guy. I like following your builds though!!
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