Digital edge finder Help

[bazmak]

I have just purchased a cheap chinese digital edge finder.20mm dia x 160mm lg,with a 10mm dia ball one end.No batteries supplied to suit postage regs
No info on what battery.Different web sites say 2 no 1.5v dry cell or size N
1 size N will physically fit but not 2.Anybody have one please can you tell me
how many batteries and what size.Does the item need 1.5 v or 3v as a
lithium CR2 seems to be the correct physical size.Any help much appreciated
Regards barry

 

[digiex-chris]

I don't know exactly, but just a thought. Considering that typical LEDs of that type require 1.2 to 1.6v, and that there's no funny electronics in side (it's just making a connection between an LED and a battery, simple as that) I don't think it's very likely that it'll be 3v. It's difficult to determine exactly which you have, but many of these type of edge finders spec the LR1 battery, which N is the equivilent of. So one 1.5v N battery does make sense to me.

I don't think it's likely to be CR2, which is more common in older film cameras than measuring equipment. Requiring CR2 would also need limiting resistors (or multiple LEDs in series, which wouldn't make sense either for voltage drop/brightness reasons), which would be extra unneeded expense that a chinese manufacturer would be likely to try to avoid.

You can easily test it on the bench by shorting the base to the tip.

 

[Jasonb]

Looking on the net I did see one seller of the 20x160 type that had 1.5 V in the main description and 12V further down the listing. I have a 1/2" shank finder that uses the 12V A23 battery which is similar size to N.

J

 

[digiex-chris]

Looking on the net I did see one seller of the 20x160 type that had 1.5 V in the main description and 12V further down the listing. I have a 1/2" shank finder that uses the 12V A23 battery which is similar size to N.

J

ah, interesting. Well that range makes it an easy test. 1.5v won't light if it requires 12.

 

[ironman]

Can you show a picture of the one you actually have?

 

[petertha]

Hard to know without seeing your ad/specs/brochure & could be confusing depending on what they say or don't say. Here is a sample ebay ad. 2 alkaline (or NimH or NiCd) cells in series @1.5v/cell nominal = 3.0 v total to the LED. Now if you happen to have a single 3.1 volt lithium cell that fits the can, close enough, I'm sure it would work just fine. Voltage is voltage & these are negligible amp draw. But if you weren't provided the word 'alkaline' or cell voltage & popped in two Li cells because they fit, they would add to +6v. Depending on the LED & what they have for circuitry, you could be supplying too much voltage. I'm not sure about LED's, do they just burn brighter... 'to a point' or do these devices have little voltage regs built in to accommodate different cells?


3.Battery: 2 x 1.5v（size：N） alkaline battery (Battery is not included)

 

[digiex-chris]

I'm not sure about LED's, do they just burn brighter... 'to a point' or do these devices have little voltage regs built in to accommodate different cells?

They get brighter to the point that they burn out. An LED rated for 1.5v will probably work ok at 2v but have a limited lifespan, and will pop instantly at 9v. LED circuits rated for 3v or higher tend to be using driving electronics to maintain a steady output as the battery dies, or are extremely high output lights or have multiple LEDs in series. Driver circuits need source voltages higher than the voltage drop across the LED, so you usually won't see anything more than a single simple LED or multiple LEDs in parallel being sourced by 1.5 volts.

Assuming we can't identify it and find instructions, I'd start with the 1.5v N since it physically fits and is a low safe voltage (any other circuit type would require a higher voltage, not lower), and see if it's bright enough to use. If not, a CR2 might work, but if it were designed for 1.5v, I would not expect it to last long, thats why I'd test 1.5v first. N is nowhere close to 2xSR44, so I doubt that it's any combination of button cells. I doubt it's A23 (12v), as there's no need for higher voltage in something like this that is no more complicated than a flashlight. I could easily be wrong though.

 

[canadianhorsepower]

This should cover all the faces of this issue:fan:
I did include a picture and math formula on how to calculate the resistor value
If one battery fits and it's a 12 volts do the math run to radio shack get a resistor and you are in business

enjoy

 

[digiex-chris]

trouble is, we don't know if there's a resistor or regulator in there already or not

 

[canadianhorsepower]

trouble is, we don't know if there's a resistor or regulator in there already or not

fine but if you put one with the math I gave you
It want work.... to dim

 

[bazmak]

Many thanks for all your help.The device will physically accept batterie(s)
of 14 dia x 30mm lg.1 no of N size is 12mm x 30mm which will fit and give 1.5 v.1 no CR2 will fit at nom 14 dia x 30lg and give 3v.I did drop in an AA battery
shorted it out with alum foil and it did work,so unless anyone has one and can confirm size i will play safe and fit 1 no N.although the dia appears small
Question, two batteries end to end at 1.5 v each.Does this give 1.5v or 3v
Excuse my ignorance.Nothing is simple buying from China

 

[petertha]

Question, two batteries end to end at 1.5 v each.Does this give 1.5v or 3v

Two cells of 1.5 volts/cell nominal rating configured end-to-end = 3.0v total because they are in series, so additive voltage.

 

[bazmak]

So are you saying i need the lithium 3v battery ??
Which i think will physical fit. Regards barry

 

[petertha]

The example I pulled up from an ebay listing was just that, an example. It might not be the same as yours. You said "No info on what battery. Different web sites say 2 no 1.5v dry cell or size N".

So personally I'd follow what guys suggested here: start with lowest voltage, a single cell 1.5v, see if it lights. If it does you're done. If not, no harm done with under-voltage, go up to next nominal voltage which is ~3v. You can achieve that with either 2x 1.5v alkaline or nimh cells stacked end-to-end series, or a single Li cell at 3v nominal depending on what fits, or maybe just faking it with wires to test. Just would hate to see you pop the LED experimenting if the voltage was too high.

I have this one which uses a single AAA 1.5v. But that may or may not match what you have.

 

[bazmak]

Thanks petertha.The one i bought says 2 no 1.5 dry cells or size N
And one site shows 2 batteries end to end.Problem being that 2 batteries wont fit,but if 2 gives 3v then i dont understand.Maybe they are saying 2 size N are supplied,1 for the unit and 1 spare.If only some one out there has the same 1 as me.As you say if i use the 3v then i might pop the led.I have tried it with an aa battery and shorted out .The LED did light but did seem dim.No rush til i get to the shops

 

[petertha]

Thanks petertha.The one i bought says 2 no 1.5 dry cells or size N
And one site shows 2 batteries end to end.Problem being that 2 batteries wont fit,but if 2 gives 3v then i dont understand.Maybe they are saying 2 size N are supplied,1 for the unit and 1 spare.

Hmm, sounds like their advertising department could benefit from some Clarity lessons, eh? You're right, 2 could mean one spare included as in bonus offer. Sheesh.

'N' just defines the physical dimensions of the can. Just like A or AA or C have their own specific dimensions. If I understand correct, they are also known as EN90 & 9100's. I see lots of alkaline N's which are typical 1.5v & the odd rechargeable which could be NimH 1.2-1.5v. But if its offered in typical lithium then it would likely be ~3v even though same physical size.
http://www.batteriesandbutter.com/N.html?gclid=CO2Q2fHG6MUCFQORfgod3zEAtA

But stumbled on this
http://en.wikipedia.org/wiki/N_battery
http://en.wikipedia.org/wiki/A23_battery

An N-cell battery has a similar size to the A23 battery, which has a 12V output.

 

[petertha]

Thanks petertha.The one i bought says 2 no 1.5 dry cells or size N

Dry cells is another abused term. Some take it to mean alkaline, but technically it doesn't properly distinguish the possible chemistries we are wondering about. Well... I guess we know its not a lead acid wet cell car battery or squishy polymer sack.
http://en.wikipedia.org/wiki/Dry_cell

I think they should send you 2 free edge finders & a box of spare batteries for your pain & suffering!

 

[bazmak]

Thanks for your interest.Also read up on the 12v but discounted it
as i cant see any reson for 12v to light an LED.The thing is the unit only cost $12 delivered and the batteries are almost as much as the unit
At this stage i will take the unit down to the store and see which battery fits best.An ongoing saga over something no better than a cheap flashlight
Its a shame ,the unit looks to be well made from substansial stainless steel
a simple piece of paper with battery installation diagram would not have gone amiss.Will post any further results

 

[petertha]

I hear you. In fact, suspect I've probably been eyeing the similar units on ebay. Unfortunately (at least to me) the vast majority are all BIG. L=155mm (6.1"), shank dia = 20mm (0.787"), probe dia = 10mm (0.393")... which they then comically translate as 10 cm

16$ & free shipping. Sheesh, I could not buy the materials for that. But I just can't foresee myself putting that big muther in my little mill & unfortunately cannot seem to source its little brothers & sisters, typically 0.375" shank & 0.200" ball/probe. Not all, but some can go for +$100 in tool catalogs & my spider sense tells me some may well originate from the same factory with sticky middleman fingers.

Who knows, maybe they are a big flashlight can. Some less reputable vendors will attach a specs sticker to say whatever you want to hear. But I'm wondering.. why are these big ones so prevalent?

http://www.ebay.com/itm/Electronic-...300?pt=LH_DefaultDomain_0&hash=item25965d98bc

 

[Swifty]

We can buy the same item from eBay Australia site for A$16.68, which converts to US$12.75, delivered from China also. US$3.24 cheaper, nice to be cheaper here for a change.

Paul.