In response to another post, here's my procedure for converting a Pointer Cadet training beacon to use ordinary C Cell batteries instead of the $40.00 battery pack (which is really just C-Cells anyway)...
my old squadron modified a practice ELT like this and even added a charging port on the side of the ELT. Biggest mistake we ever made. We had massive problems with battery acid that eventually rendered the practice ELT nearly useless.
Quote from: CAPSGT on May 30, 2008, 05:34:10 PM
my old squadron modified a practice ELT like this and even added a charging port on the side of the ELT. Biggest mistake we ever made. We had massive problems with battery acid that eventually rendered the practice ELT nearly useless.
That sounds like possibly a problem with overcharging batteries or trying to charge non-rechargeable batteries. What kind of batteries burst? One of our members contacted pointer about a replacement battery one time and the person said that C batteries can be used.
couldn't really tell you at this point. I wasn't around until the thing was almost dead and that was several years ago. I didn't pay enough attention to what kind of batteries they were as I was concerned with looking at the condition of everything on the inside. Either way, I'm a bigger fan of sticking with stock parts. The Pointer 2020 battery is less than $30 and is a breeze to install
Pointer themselves recommends using C-Cells with their trainers. It's even on their web page for the product. What I would NOT do is add a charging port for rechargeable batteries as you would also have to design an overcharging circuit. Plus, you (technically) violate the National guideline against modifying the unit (and I checked - the battery mod is fine since you don't alter the unit itself - it can always go back to stock batteries).
I just got done fixing our practice beacon, we lent it to another squadron and when we got it back someone had tried to fix it. It looked like a kindergartner had gone in there with a soldering iron. Who ever had originally configured the set up determined that there needed to be 6 D cell batteries. To me that seems like a lot, I was thinking about reducing it to 4 but wanted to see if anyone knew if there was a reason it needed 6. ???
Nope. Pointer will tell you that it requires 5; this is what is in their battery packs as well.
Joe,
Great illutstrations. You should ask Scott to put those up on www.cap-es.net with some of the other projects over there.
Quote from: JoeTomasone on June 07, 2008, 12:09:11 AM
Nope. Pointer will tell you that it requires 5; this is what is in their battery packs as well.
A fresh, new room temperature AAA, AA, C, or D cell can put out approximately 1.2 V. The difference is how long each type can supply that voltage.
The C cells are connected in series to produce about 7VDC (1.2v per cell x5).
Pointer states:
"If you want to simulate a beacon with a weak battery, you can
use a nearly dead battery in the 1‐C Cell holder; that will drop the supply voltage and produce a weaker signal." That would drop it around 6V and some change. So output power is effected by supply voltage.
Adding a 6th cell could raise the input voltage to nearly 7.5v. Probably not enough to damage the components but possibly exceeding the maximum allowed output power and/or overdriving the circuit and producing a "dirty" signal (causing interference). Both of which can lead to some nasty fines.
Actually, the unit is rated by Pointer for 7.5vdc. Most common alkaline batteries are now rated for 1.5vdc (check energizer.com and duracell.com, for example). I took a set of Energizer Max C-Cells out of the pack and measured them - 1.6vdc.
http://www.pointeravionics.com/product.php?pid=138 (http://www.pointeravionics.com/product.php?pid=138)
"Also, for home made battery packs, we suggest a maximum of 8 volts for supply."
At 1.6v per cell x 6 = 9.6v
Bottom line - running a transmitter out of spec (using 6 cells instead of 5) is not "A Good Thing".
Quote from: wacapgh on June 10, 2008, 06:51:10 PM
http://www.pointeravionics.com/product.php?pid=138 (http://www.pointeravionics.com/product.php?pid=138)
"Also, for home made battery packs, we suggest a maximum of 8 volts for supply."
At 1.6v per cell x 6 = 9.6v
Bottom line - running a transmitter out of spec (using 6 cells instead of 5) is not "A Good Thing".
Correct, but the plans I've posted call for 5 batteries. Again, this is precisely what is inside the $40.00 Pointer battery - 5 C Cells. These plans simply make it so that you can use store-bought C cells, which are vastly cheaper and easier to find.
1.6v per cell x 5 = 8.00v.
Scroll up about 6 posts - Lt Rudin was telling us about another squadron having modified his squadron's uint to run on 6 cells and wondering if that was a good idea.
Just trying to present some facts to back him up. :)
Quote from: wacapgh on June 11, 2008, 08:02:44 PM
Scroll up about 6 posts - Lt Rudin was telling us about another squadron having modified his squadron's uint to run on 6 cells and wondering if that was a good idea.
Just trying to present some facts to back him up. :)
Correct, but you stated:
Quote from: wacapgh on June 09, 2008, 08:21:48 PM
Adding a 6th cell could raise the input voltage to nearly 7.5v. Probably not enough to damage the components but possibly exceeding the maximum allowed output power and/or overdriving the circuit and producing a "dirty" signal (causing interference). Both of which can lead to some nasty fines.
I didn't want him thinking that since the unit is rated for 7.5v and will tolerate a maximum of 8v (1.6v x 5) that a 6th cell was OK since that's really 9.5v.
If you go the rechargeable battery route, you should be able to hook on a small solar panel to extend the life of the batteries. I found it really, Really, REALLY annoying that on the last training mission I was on we searched 3/4 of a grid (by vehicle) for two and a half hours looking for a target with dead batteries.
I found these $9, 4.5v panels that would fit perfectly on the top of a Pointer Cadet
http://www.solarhome.org/index.asp?PageAction=VIEWPROD&ProdID=14
Voltage: 4.5
Watts: 0.4
Current: 66.67
Size: 3.35" x 2.6"
You'd need two of those.
Quote from: JoeTomasone on June 12, 2008, 04:44:10 AM
You'd need two of those.
That would go over the voltage, and good luck fitting them both nicely on the beacon. I'm talking about extending the life, not running the beacon indefinitely on solar. I haven't found a panel of good dimensions with a high enough output.
Quote from: ♠SARKID♠ on June 12, 2008, 04:49:39 AM
Quote from: JoeTomasone on June 12, 2008, 04:44:10 AM
You'd need two of those.
That would go over the voltage, and good luck fitting them both nicely on the beacon. I'm talking about extending the life, not running the beacon indefinitely on solar. I haven't found a panel of good dimensions with a high enough output.
Although if you line these two in a circuit, you'd get 7.5 and possibly stay small enough to fit on the beacon.
http://store.sundancesolar.com/minsolpan6v5.html
http://store.sundancesolar.com/minsolpan15v1.html
You have to charge with higher voltage than the supply. 8v batteries would charge nicely with 9v.
However, a 4.5v battery would only charge a pack lower than 4.5v - which likely is too weak to effectively power the trainer. You aren't extending the pack much since all of the power the panel provides is wasted until the pack is about half-strength, and since that panel is putting out 80mAh and the trainer is using 150mAh, it's pretty much next to worthless.
Quite frankly, at a cost of roughly $7.00 to put fresh alkalines in the trainer, why bother?
QuoteYou have to charge with higher voltage than the supply. 8v batteries would charge nicely with 9v.
However, a 4.5v battery would only charge a pack lower than 4.5v - which likely is too weak to effectively power the trainer. You aren't extending the pack much since all of the power the panel provides is wasted until the pack is about half-strength, and since that panel is putting out 80mAh and the trainer is using 150mAh, it's pretty much next to worthless.
Fair enough, learned something new today.
QuoteQuite frankly, at a cost of roughly $7.00 to put fresh alkalines in the trainer, why bother?
To prevent death in the field; I've had it happen. And besides, it makes for a neat project and is just that much cooler :)
Quote from: ♠SARKID♠ on June 12, 2008, 06:17:35 AM
To prevent death in the field; I've had it happen. And besides, it makes for a neat project and is just that much cooler :)
Granted, but remember, you can measure the voltage of the pack before you start the training. If you need replacements, slap 'em in. The UDF gear box that I carry has C-cell batteries ready to go for that reason.
I'd go with a solar charger and a spare set of rechargeable C-cells. While one set is running the beacon, the other is charging. Swap as required.
We started a project to modify one of our ammo can beacons. One of our gurus has over 400 lines of C code written to "turn off" the beacon using an onboard clock at a pre-defined time. This would allow for the beacon to be set and placed the night before and then "wake up" and start operating the next morning for the SAREX or however one wanted to program it.
We were also experimenting with disabling the modulation and just leaving the carrier to be really tricky... Never implemented either... >:D