Discussion: Getting Rid of 9V Batteries for my Pinpointer (continued)

I wrote a blog post a while back showing my initial attempt to get rid of a 9V battery for my Minelab Pro-Find 35. Since then, I’ve revised my design a few times. The revisions weren’t to improve performance, but instead make it less cumbersome to use.

The purpose of this blog post is to document and share some of these revisions, as well as show you the final iteration. This final iteration still has room for improvement, but for now, I think I’ll settle on its design.

First Revision

I basically just took the wiring and cleaned it up some so it was more compact and contained. I’ll just let me pictures do the talking:

Second Revision/Garrett Carrot

I later was able to pick up a Garrett Carrot as a part of a Equinox 600 package deal I purchased. So I decided to work on this battery conversion so it would work in that pinpointer. I also wanted to do away with the lithium battery. This lithium battery, if not properly maintained (stored with sufficient charge), would literally go bad just sitting in storage.

Perhaps there was some other maintenance I could have done to protect the lithium battery, but I didn’t want a high maintenance battery. So I decided to start using rechargeable NiMH AAA cells. Below are the pictures that show what I did. 

The Third Revision

This worked in both the Garrett Carrot (Pro-Pointer AT) and Minelab Pro-Find 35.

The Fourth Revision

I’ll begin by just showing you the final set up. This is designed for the Garrett Carrot, although it should work in the Pro-Find 35. I can’t confirm the latter as I recently sold that pinpointer because I didn’t need two virtually identically performing (for my purposes) pinpointers.

That last picture is just for kicks. Maybe one day I’ll paint the battery endcap extension green and make the Garrett Carrot look even more like a carrot.

This will run off of alkaline, lithium AAA primaries (with about 1.7 nominal volts), NiCd or NiMH cells. So basically, if you have a AAA cell, it’ll work with this adapter. I primary use it with LSD NiMH cells. This adapter is also reverse compatible in that if I wanted to use the Garrett Carrot with a regular 9V battery, I could. All I would need is a special spacer (wad of paper, piece of foam, etc.) to serve as a filler in the extended battery endcap.

And yes, watertight integrity is maintained even with the battery endcap extension.

Drawbacks

Besides the obvious change in form factor, there are only 2 drawbacks. First, there is the reduced runtime. You can see my prior blog post for a discussion about it, but it’s not a problem as this should easily last an entire day’s worth of hunting (I can recharge at night).

The second drawback is the biggest one (in my opinion). It’s the parasitic electrical draw that the 9V booster chip pulls. Based on my testing, 3 fully charged AAA NiMH cells (about 800 mah of capacity per cell), will be completely dead (as far as the pinpointer is concerned) in about 3 to 4 weeks.

So this is why there’s that red wire and black plug on the side of the adapter. This serves as a switch. I could actually install a switch, but I didn't have a small enough one on hand and I didn’t feel like spending $5 in shipping for a 75 cent (or so) component. But during my next order for electronic components, I'll add a small switch to my order. When the red wire is disconnected, the batteries should last years in storage (they’re Eneloops) and still be ready to go when the time comes. So far, it’s lasted 7+ weeks without any noticeable parasitic power drain.

Now What?

The first major step in removing 9V batteries from my metal detecting gear is done. I’m currently working on using a 4x AA cell rechargeable battery pack to replace the dual 9V battery setup in my Fisher F2.

Discussion: Getting Rid of 9V Batteries for my Pinpointer

LiPo with 9V voltage booster for Minelab Pro-Find 35

I really like batteries, with the exception of the 9V battery. It’s expensive and has poor performance with respect to its internal resistance and capacity. In my opinion, nothing designed after 2010 should be using a 9V battery. Maybe some of you out there can think of a reason as to why a particular device, such as a multimeter or smoke detector should still use a 9V battery, but I doubt that’s possible. And if it is possible, it will be an exception.

I also enjoy metal detecting. However, my metal detector (Fisher Research Labs F2) and pinpointer (Minelab Pro-Find 35) both use 9V batteries. My next metal detector will use AA (Garrett AT series or Fisher F75) or a built in lithium (a la Minelab Equinox), but until then, I’m stuck with 9V batteries…or so I thought.

What’s a Pinpointer?

For you readers out there that aren’t familiar with metal detecting, a pinpointer is a handheld device that helps pinpoint a metal object in a hole or plug you just dug. You don’t have to have it while metal detecting, but it saves a lot of time.

The majority of the pinpointers on the market today use 9V batteries. The three major exceptions are Fisher Research Labs’ F-Pulse, White’s Bullseye TRX and XP’s MI-4 and MI-6.

I set out to create an add-on that would allow my Pro-Find 35 to use something other than a 9V battery. This blog post sets out how I did it.

The Set up

A picture is worth a 1,000 words, so I’ll start with pictures (they're upside down for some reason).

The connectors I’m using are Deans and the blue thing on the right is the voltage booster itself. Here are some of its more notable specs and pics:

Minimum operating voltage: 2.5v

Weight: 0.4g

Maximum quiescent current: 2ma

Minimum input current: 1.4a

Switching frequency: 1.3 khz (PWM control)

Here’s a link to where the item itself, in case you want to order one or learn more about it:

https://www.pololu.com/product/2116

Below are some pictures of it installed in my pinpointer:

Performance

I have not tested this in real world conditions, just indoors using the “hour glass and coin” method. Below you can see how it performs with the stock 9V battery:

I didn’t mark the cardboard, but when using the nickel and the voltage booster, the sensitivity improved by about 1-3 mm, i.e. the hourglass enlarged by about 1-3 mm in all directions except the middle bottleneck.

As for run time, that depends on the battery used. I’m currently using what’s in the pictures and it has 750mah in capacity at 3.7 nominal volts. Fully charged it’s around 4v. Using some rough math, this voltage booster is the rough equivalent of a 9V battery with 330mah of capacity. The typical 9V alkaline battery has about 550mah. Therefore, you can expect about 60% of the run time of whatever you’d get with an alkaline 9V battery. But there are at least two caveats to my numbers.

First, the efficiency of the voltage booster. I don’t know what it is, but I wouldn’t be surprised if it’s around 85%-90%. If I’m wrong, feel free to comment.

Second, the relatively low resistance of my set up. When using the stock 9V battery (it’s heavy duty, not alkaline), the battery has trouble delivering the current necessary when the pinpointer goes off. I know this because the LED slightly blinks rapidly. But this voltage booster set up does not result in the LED light slightly blinking at all.

I think my use of a much higher performing battery than the 9V battery (heck, almost any battery will do better than a 9V) at least partially compensates for the efficiency loss of the voltage booster. I think this compensation effect will still exist when using an alkaline battery instead of a heavy duty, although the effect will be less.

What Are the Advantages and Disadvantages of the 9V Booster?

The sole advantage is that you don’t need to use 9V batteries any more. This can make organizing your battery supply that much easier and save money on an expensive battery type. For some of you metal detectorists out there, this might allow you to completely remove 9V batteries from your metal detecting set up.

Numerous disadvantages include:

- You need a special charger. A typical R/C hobby style charge that can handle LiPo cells should suffice.

- It’s a bit janky, at least compared to a self-contained 9V battery. I intend to clean things up a bit as I tweak this design. I should be able to get most of everything to fit inside a gutted 9V battery.

- At least slightly lower capacity/run time. I don’t know this for sure, but I will assume this is the case for now. Under real world conditions, I wouldn’t be surprised if the run time is about the same with my 1S 750mah LiPo battery.

- If you want to avoid using a special charger and use drop-in AAA cells, you need to permanently modify your pinpointer. In my case, I’d need to cut a large hole in the end cap and effectively lengthen it to accommodate the AAA battery holder like this one:

It won’t be hard to do, but I don’t want to do anything to permanently modify my pinpointer while it’s under warranty.

Bottom Line

For most of you, it won’t be worth using this voltage booster. If you already have a hobby R/C charger and soldering tools and supplies, then you might enjoy this little project and can save some money in the long run by getting rid of 9V batteries

But if you hate 9V batteries as much as I do, you’ll definitely want to consider this.

Discussion: Epinephrine Autoinjectors

Attribution: Jfoldmei per Creative Commons Attribution-Share Alike 3.0 Unported license.

Disclaimer: I’m not a doctor. Please use the following blog post for informational purposes only and not as medical advice. Any questions or concerns should be directed to your doctor or other appropriate medical professional.

Epinephrine autoinjectors (sometimes referred to as the brand name, EpiPen) aren’t the typical outdoor gadget, but for some with severe allergies, it might be the single most important thing they take with them when they head to the outdoors or leave the house (well, except for maybe their keys and phone).

I’ve recently taken a fascination with these marvels of engineering and I want to take this opportunity to provide a brief overview of epinephrine autoinjectors for those who might be confused, curious or seeking more information about something they have to carry everywhere they go.

What’s an Epinephrine Autoinjector?

An epinephrine autoinjector is a unique type of syringe that automatically injects epinephrine into an individual. Unlike a regular syringe, autoinjectors are special because they already have a preloaded dose of medication and contain an internal mechanism that allow the user to inject the medication without having to see the needle or press down on a plunger.

In the United States, epinephrine autoinjectors usually come in two doses: 0.3 mg for adults (or anyone who weighs 66 pounds or more) and 0.15 mg for children (or anyone weighing between 33 and 66 pounds). There’s also a 0.1 mg dose for infants and toddlers (or anyone weighting between 16.5 and 33 pounds), but it’s not as common.

Why Do We Have Epinephrine Autoinjectors?

The primary purpose of epinephrine autoinjectors is to deliver an emergency injection of epinephrine (also known as adrenaline) to an individual suffering a severe allergic reaction, specifically anaphylaxis. Anaphylaxis has a variety of symptoms, but the most serious include swelling of the throat, fainting and trouble breathing. In rare cases of anaphylaxis, death can occur.

For more information about anaphylaxis, I encourage you to check out the following online resources:

https://www.webmd.com/allergies/anaphylaxis#1

https://www.foodallergy.org/life-with-food-allergies/anaphylaxis

Types of Epinephrine Autoinjectors Available

A few years ago, there was pretty much just one option for anyone looking for an epinephrine autoinjector: the EpiPen. Now, there are many more options, most of which are cheaper. I’ll go over most of the epinephrine autoinjector options available (or soon to be available) in the United States.

Amedra Pharmaceutical’s Adrenaclick

Caption: Adrenaclick with 0.15 mg dose

Attribution: https://www.cnbc.com/2017/04/25/kmart-pharmacy-sharply-cuts-price-of-adrenaclick-competitor-to-epipen-anti-allergy-device.html

To be honest, I don’t think this is still available for sale in the United States and if so, I don’t know how easy it will be to obtain. But I still want to mention it because it’s closely related to a current and past version of an epinephrine autoinjector.

The past version is the Twinject. I don’t know the exact relationship between the Twinject and the Adrenaclick, but they are based on very similar designs. What made the Twinject special was that it has an internal syringe could be removed to provide a second dose of epinephrine if necessary.

Caption: Twinject, “adult” version with the 0.3 mg dose.

Attribution: http://dxline.org/drug/medicament/23830/

The current version of the Adrenaclick is its generic equivalent. Who makes it is a bit confusing, but I think it’s either Impax, Lineage or Amneal. My understanding is that Impax acquired the rights to Adrenaclick and then merged with Amneal. And Lineage is (was) a whole-owned subsidiary of Impax. You can see what it looks like below:

Caption: Generic version of the Adrenaclick in both the 0.15 mg and 0.3 mg doses

Attribution: https://epinephrineautoinject.com/

With some MacGyver-ing, you can get a second dose of epinephrine relatively easily from the generic version of the Adrenaclick (and the EpiPen). Just keep in mind this is an improper (and possibly illegal? I don’t know) use of this medication. But in an extreme emergency where medical care is hours or days away and a second injection is needed, it’s an option.

Mylan’s EpiPen

Just to set the record straight or clear up any confusion, “EpiPen” is the brand name of a particular type of epinephrine autoinjector. Specifically it’s the epinephrine autoinjector made by Mylan. Many people, including doctors, will use the term EpiPen to reference any epinephrine autoinjector.

If the name and device sounds or looks familiar, it’s because they got a lot of bad press recently about price hikes on the EpiPen when there was no alternative available and many customers felt like they were being price gouged. Whether Mylan was acting unethically or were just acting as a business savvy company, I’ll leave it up to you to research and decide on your own.

Caption: The older version of the EpiPen. Its overall design might look familiar to those who have served our country in the Armed Forces.

Attribution: Sean William per Creative Commons Attribution-Share Alike 3.0 Unported license.

Caption: Current version of the EpiPen, 0.3mg dose

Attribution: Author’s own work

The EpiPen probably has the largest share of the epinephrine autoinjector market, thanks to the efforts of Mylan. If you know someone who carries an epinephrine autoinjector, chances are pretty good they’re carrying the EpiPen. There are also more accessories specifically designed for the EpiPen, such as smart cases that link to a smartphone and provide a host of features such as notification of activation.

Mylan’s Authorized Generic Version of the EpiPen

Mylan now has an authorized generic version of the EpiPen. It’s exactly like the EpiPen except for the sticker/label put on the epinephrine autoinjector. According to the FDA, an authorized generic is EXACTLY like the brand name version, except the brand name doesn’t show up on the products label. You can see the below pictures to see how similar they look to the actual EpiPen:

Caption: Authorized generic versions of the EpiPen, 0.3mg (yellow) and 0.15mg (green) doses

Attribution: http://newsroom.mylan.com/2016-12-16-Mylan-Launches-the-First-Generic-for-EpiPen-epinephrine-injection-USP-Auto-Injector-as-an-Authorized-Generic

One feature of the EpiPen is that after injection, the orange plastic tip will protrude from the bottom of the EpiPen so the needle is covered and not exposed to the user or anyone else.

Sanofi’s AUVI-Q

The AUVI-Q is the new kid on the autoinjector block, although it’s been on the market (off and on) for the past few years. It has three features that separates it from other epinephrine autoinjectors. First, it’s shaped like a really, really thick credit card. This shape can make it easier to carry around for some users.

Second, it talks and provides step-by-step prompts and information to users. According to Sanofi, the AUVI-Q has a higher percentage of successful use when users have little to no training. Basically, it’s a square shaped epinephrine autoinjector with a built in speaker.

Third, it comes in a 0.1 mg dose for infants and toddlers. Most of you reading this probably won’t need a dose this small, but it’s available for the small minority who might have a small one with a documented severe allergy.

Caption: Auvi-Q, the “talking” autoinjector in the 3 doses it’s offered in

Attribution: https://www.auvi-q.com/about-auvi-q

Teva’s Generic Version of the EpiPen

At the time of writing, this may have only been on the market for a few weeks. It’s similar to the EpiPen in overall appearance and function, but there are two main differences.

First, it doesn’t come with a case. Instead, it has a cap covering the part where the needle comes out. Second, the blue safety release comes off in a slightly different manner.

Caption: Teva’s generic version of the EpiPen in both the 0.3mg and 0.15mg versions

Attribution: https://www.tevaepinephrine.com/howtouse

Adamis Pharmaceutical’s SYMJEPI

I believe this one still hasn’t reached pharmacy shelves, but it’s really close from my understanding. Its main selling point is supposed to be its lower price than most epinephrine autoinjectors. The main reason for this is probably that it’s not really an autoinjector, but rather, a preloaded syringe.

Caption: The Symjepi (Note: may not be a picture of the final product)

Attribution: https://snacksafely.com/2018/10/additional-symjepi-dosage-strength-approved-for-anaphylaxis-treatment/

To learn more about these various types of epinephrine autoinjectors, I recommended you check out Dr. Julie Brown’s Youtube page. She posts many videos showing most of these autoinjectors in action and other useful and interesting information relating to them.

Which One to Use?

That’s not an easy question to answer. Each one has its advantages and disadvantages, but what’s an advantage to one user may not be an advantage for another user.

For example, buying Teva’s EpiPen generic will save money, but for those who have hit their out-of-pocket limit on their health insurance, that feature won’t matter. Instead, they may still want the brand name EpiPen due to its familiarity to the general public and the greater number of accessories available (such as special cases). And when cost is a serious concern (such as those without insurance), the SYMJEPI might be the best option. However, it will not be an autoinjector and for those with a fear of needles or who might need others to assist in the injection, this could be a deal breaker.

As another example, if a young child has to carry an epinephrine autoinjector, the AUVI-Q might be the best one to use because of the high probability a teacher, childcare provider or complete stranger may be the one who will actually provide the epinephrine injection. The talking instructions could be crucial to an untrained individual.

Then there’s the availability of certain devices. Some pharmacies may have one version, but not the other. Anyone who needs to carry an epinephrine autoinjector should probably talk with their doctor and discuss their options. Some of these might be available directly from the pharmaceutical company for those who don’t have a nearby pharmacy that carries it.

Bottom Line

This blog post wasn’t intended (nor should it be interpreted) to provide a recommendation as to which epinephrine autoinjector to use. Rather, it hopefully provides more information so individuals can ask more informed question to their medical care providers.

Review: Oppama PET-304 Tach

If you want to objectively tune or troubleshoot your small two-stroke engine, you need a tachometer (tach). There are many options to choose from, but I choose to purchase Oppama Industry Co., Ltd.’s PET-304 since I saw some prominent lawn and small engine youtubers using it. I believe it’s also the same the Echo branded one, just without the Echo brand name stamped on it. Finally, I was also able to find a good deal: less than $62 shipped from Weingartz.

What’s in the Box?

I could tell you, but I’ll let my pictures do the talking:

Caption: This picture posts upside down for some reason.

Specifications

RPM Range: 100 to 20,000 RPM

Accuracy: plus or minus 10 RPM

Accessories: Inductive pick up lead (included)

Weight: 29 grams

Updated readings: Every 0.5 seconds

Wired or Wireless?

When watching youtube videos of engine tachs, people simply hold the tach up to their engine and take a reading. But when searching online, most of the tachs have wires that attach the tach to the spark plug wire.

To clear up any confusion, you can take RPM readings with or without the wire. I choose to use the wire to get what I would presume would be more consistent readings. So instead of the holding distance varying depending on the engine and spark plug placement, I can just use the wire to make things more straightforward.

Caption: This is how the instructions say to connect the wire to the tach.

Attribution: Author’s Own Work

How Does it Work?

Exactly how you think it would. Just clamp the wire to the spark plug wire (ignition lead) and the tach will do the rest; it even turns on automatically when it’s close enough to the engine (1/2” to 12”) or is connected to the ignition lead.

There’s also no accessible battery compartment. Apparently this isn’t designed to have its battery replaced. Initially this bugged me, but the battery should last 20,000 hours. To put that in perspective, that’s more than 830 days of continuous use.

Here’s a picture of me taking a reading on an Echo PB-251: 

I also used it on my other machines, including my Echo CS-271T top handle chain saw and my Bolens BL110 string trimmer and it worked without issue.

Other Notes

Based on the pictures in the instruction manual, the PET-304 appears to be water resistant, so you can presumably use it in the rain without issue. However, the instructions also say to avoid getting the inductive lead wet or letting it touch anything during a reading. So if you want to use this in the rain, you’ll need to do so without the inductive lead. There is also a hour-meter function that keeps track of how long it’s been used.

Conclusion

Anyone in the market for a name brand, high quality tach should consider the PET-304. It’s a bit pricier than some models, but it’s a great addition to anyone’s toolbox or workshop.