Rewiring the Datel Digital Voltmeter

[Constant Mesh]

To simplify your circuit a bit more you can easily use the horn switch or starter switch as your momentary switch. I assume the momentary switch would be used only when the ignition was switched off so there would be no voltage drop in the return circuit except for the VM current.

Both of these switches connect their loads to the common return circuit. Either circuit would be easy to tap although the horn circuit might be the most accessible. I would prefer the starter switch since its load is the starter relay coil, a small load of 100 ma or so. If the horn current was partially diverted through your new relay it might damage the relay contact. This couldn't happen if the starter switch was used.

Why punch another hole in something to mount a momentary switch?

 

[Constant Mesh]

The relay contact's minimum current rating may be of concern in this application.

"It has been found that a small amount of periodic arcing can actually be good for the switch contacts, because it keeps the contact faces free from small amounts of dirt and corrosion. If a mechanical switch contact is operated with too little current, the contacts will tend to accumulate excessive resistance and may fail prematurely! This minimum amount of electric current necessary to keep a mechanical switch contact in good health is called the wetting current."

"Normally, a switch's wetting current rating is far below its maximum current rating, and well below its normal operating current load in a properly designed system. However, there are applications where a mechanical switch contact may be required to routinely handle currents below normal wetting current limits (for instance, if a mechanical selector switch needs to open or close a digital logic or analog electronic circuit where the current value is extremely small). In these applications, is it highly recommended that gold-plated switch contacts be specified. Gold is a "noble" metal and does not corrode as other metals will. Such contacts have extremely low wetting current requirements as a result. Normal silver or copper alloy contacts will not provide reliable operation if used in such low-current service!"

The voltmeter current is less than 10 ma. This is likely less than the relay's minimum current rating.

 

[Fairlaner]

C'mon Fred. You're late to the party!

No relay however, just a switch. Fukin engineers! Always making things more complicated! <img src="https://www.fjrforum.com/forum//public/style_emoticons/<#EMO_DIR#>/tongue.gif" style="vertical-align:middle" emoid=" " border="0" alt="tongue.gif" />

<img src="https://img.photobucket.com/albums/v637/SkooterG/farkles/Datel2.jpg" border="0" class="linked-image" />

Greg they would look better if'n they were straight...........

R

 

[Fred W]

Good point. I have not noticed any problems yet, but who knows how long it will take for the contacts to get crusty?

So, for this app we need a weather-sealed 12V SPST relay with gold contacts. Know of any?

[edit] Looks like I'll be searching for a replacement switch for my meter setup shown above too. The one that I currently have was just a cheap one from Rat Shack and is not weather tight. Last time I left it in a hotel parking lot in the rain (uncovered) the meter turned itself on when the switch was still off. It doesn't seem to mind riding in the rain and actually moving. It's the pooling water standing still that leaked into the switch innards.

PPS - Skootie's switch hole looks like it might be a little too big for his switch? Jus' sayin'...

 

[wfooshee]

I put mine in the top of the C panel, more in line with the eye's regular gauge scan. Won't fit flush because of the windshield mechanism behind it, but that didn't matter to me. It sits partially recessed, and I used black RTV to "glue" it in place.

Mine's wired with a relay so it's on with the key, nothing else on that relay. The gear indicator above the LCD panel is no longer there. It didn't survive long in the rain.

 

[FJRGuy]

This is a timely resurrection of an old thread for me too! I am in the process of installing my Datel Clone as well. I basically have Fred's "cake and eat it too" approach as well but am having a better cake adding a glass of good Port!

I'll try to provide a diagram for clarity and photos as I progress but here's the concept:

I too am using a relay to switch a direct connection to the battery. After reading this, it makes sense to me to switch the negative side of the meter.

I have a ON-OFF-(ON) switch feeding the relay.

Input to the (ON), momentary, side of the switch is un-switched power allowing me to check the battery voltage without the ignition on but not allowing it to be left on accidentally.

Input to the ON side of the switch is switched power allowing the meter to be on when running but adds the ability to turn off the meter while running as well (the better cake).

The "Port" part of my plan is adding a connector (style TDB) for test leads so I have the ability to use the VM for roadside troubleshooting. Yeah, I know it's not as useful as my DMM, but for the amount of times I may need it, it seems better than carrying my DMM all the time.

The VM, switch, relay, etc... will all be mounted in a small 'project box' suitably mounted to the bike and powered by a 3 wire lead

I'm sure this solution will be too complex for some people's preferences but... I think it's an 'elegant' (as we engineers like to call it) solution and I like it!

 

[Fred W]

Wow... Talk about your Datel one upsmanship!

Nice.

 

[Ignacio]

I have a ON-OFF-(ON) switch feeding the relay.

Input to the (ON), momentary, side of the switch is un-switched power allowing me to check the battery voltage without the ignition on but not allowing it to be left on accidentally.

That's elegant....I didn't know they even made ON-OFF-(ON) switches and gonna have to look at that myself.

 

[ionbeam]

Wiring Products is just one of many sources:

Gentleman's glove friendly rocker, weather resistant ON-OFF-ON SPDT



Weatherproof marine toggle ON-OFF-ON SPDT



This site has just about anything you would need for wiring, including this handy headlight relay socket with pig-tail

 

[wfooshee]

I have a ON-OFF-(ON) switch feeding the relay.

Input to the (ON), momentary, side of the switch is un-switched power allowing me to check the battery voltage without the ignition on but not allowing it to be left on accidentally.

That's elegant....I didn't know they even made ON-OFF-(ON) switches and gonna have to look at that myself.

This switch from RadShack would give you push-button unswitched and normal switched power to the voltmeter, without an off. Push to see volts without the key, otherwise voltmeter works with the key. N.C. to switched power, N.O. to unswitched, common to the relay coil.

Voltmeter will turn on with the key, but can be viewed any time by pushing the button. Who needs an "off" position, anyway?

 

[Constant Mesh]

I believe the best solution is using the starter PB switch in conjunction with a relay.

I sketched a simple circuit which would work very well in this application. But I don't have a method for submitting it for your perusal.

The positive side of the relay coil connects to a switched power source, whatever one chooses to use. The negative side connects to the negative return bus. A fused (3 A) lead from the battery's positve terminal connects to the positive terminal of the voltmeter. The negative terminal of the voltmeter connects to the center common connection of a one pole double throw relay. The normally open contact connects to the battery's negative post. The normally closed contact taps (parallels) into the starter PB circuit just above the starter PB switch (opposite side from the negative return bus).

When the ignition is switched off you can press the starter PB and get a voltmeter reading with minimal voltage drop (negative bus drop for 7 ma). When the ignition is switched on the starter PB is isolated from the voltmeter and the voltage at the battery is continuously measured.

I like this scheme because the weatherproof starter PB is utilized.

A recommended relay is:

https://relays.tycoelectronics.com/pnb.asp

Click on the R10 General Purpose Relay and review the Z Type Contact Style. This contact has a minimum current rating of 1 ma and would be an excellent choice for a voltmeter application.

Of course one could always parallel a resistor with the voltmeter and bump up the current flow a little to satisfy the relay's minimum current rating. You would incur a bit more voltage drop with a resistor.

 

[Fred W]

The R10 relay you point to doesn't look like it is either weatherproof or ruggedized for an application like on a bike. That is why I chose one of the omnipresent (way too large ampacity) 30A 12V auto relays. I guess as soon as I see a problem with contact resistance I'll worry about it, but for now it seems to be working very well.

As a possible alternative, when I had an Aprilia Pegaso, I noticed that they had some nice compact 12V SPST relays they were using for all sorts of applications. I used one on mine for the sidestand bypass relay to allow the bike to idle on the sidestand in neutral, something that was not possible with the stock interlock nannies.

It isn't as cheap (at $15) as the regular 30 amp ones you find all over for $5, but it is considerably smaller and just as rugged.

Here's the post on AF1 forum where I installed it. Has the part numbers, pics of the relay and source info.

 

[ionbeam]

There are relay options. One is a solid-state MOS-FET type relay; 100% rugged and sealed with very low ON resistance. Next is a mercury wetted relay; usually hermetically sealed and the contacts don't bounce. Hg relays are pretty pricey. And finally, 'Small Signal Relay' (that phrase is the name) are relays with very low contact resistance and usually made with Ag/Au contacts that retain conductivity for >100k cycles. Small Signal Relays are also typically hermetically sealed but the reeds and coil are not ruggedized.

An automotive relay, such as the headlight relay is ruggedized for vibration and temperature. When used as intended for headlights, you don't want the contacts to vibrate and perhaps separate or the coil to reach the Curie Point and release.

 

[Constant Mesh]

The R10 relay works fine on the FJR. I've had three of them installed for over six years on my FJR with no problems. I wrapped them in a small sheet of plastic to keep any moisture out.

 

[fljab]

Wiring Products is just one of many sources:

+1; thanks!

 

[txvoyager]

I know the thread is a little old, but I would think that these volt meters are something that new FJR owners look at on a pretty regular basis. I installed it in a little different location. I also installed a matching (ambient temperature) thermometer next to it. It's not the most easily seen location, but neither the temp or voltage are things that I spend a lot of time looking at. BTW, this one is not branded as Datel, but I'll bet it's made in the same production facility. I bought this one for half the cost at Cyclemax.

 

[wfooshee]

nobody can use that spot 'cept us 2003 riders, 'cuz the rest have that annoying unlockable/unopenable box there. I put mine in the top of the C panel, so it actually faces me, instead of facing the sky or my knee.