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Rat Zapper Power Supply

Discussion in 'Power Electronics' started by Heimhenge, Jul 12, 2011.

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  1. Heimhenge

    Heimhenge

    13
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    Jul 12, 2011
    I've been having problems with mice in my attic, and have been looking at one of those new electronic traps: http://agrizaprzu001.us/

    The only problem is it requires 4 D cell batteries, and I'm concerned about battery life since it gets pretty warm up there in the summer (I'm in Arizona).

    So I'm wondering if I could mod the device to run off a 110 VAC to 6 VDC transformer, since there is an outlet up there that's available. Of course, the mod would void the warranty, but I'd be willing to risk that.

    My question is this. I understand that no rectified transformer puts out a perfectly flat DC. I'm guessing that this rodent killer uses a simple inverter and transformer to step up the voltage to what is needed for a kill, and shouldn't be as sensitive to a little ripple in the DC as some electronics. The manufacturer could not answer my question, and could not connect me with their engineers.

    Any thoughts or insights would be most appreciated. Thanks.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,411
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    Jan 21, 2010
    It would be wise to check the maximum current the device draws. I suspect that happens just after the device is "triggered". Get a 6V adapter rated for a higher current than the maximum you see.

    It will probably work fine from a plugpack. If you can get a switchmode regulator it will have far less ripple. The easy way to tell is the switch-mode power supplies are lighter, and often have a wide range of input voltages, say 90 to 265 VAC.
     
  3. Heimhenge

    Heimhenge

    13
    1
    Jul 12, 2011
    Thanks for the reply Steve. Unfortunately, I've been unable to find schematics or power specs for this unit. It's designed to run on 4 D cells, and I guess they figure that's all the consumer needs to know.

    They do claim it will run on "idle" for a year on one set of batteries, or for 30 kills, whichever comes first. That only helps minimally. 4 D cells would provide about 5000 mAh, so with no kills, it should idle at 0.6 mA. But that assumes the D cells are in series, which is just a guess.

    After a kill, I'd assume it will be recharging a large capacitor, so you correctly point out that this would be the largest current draw, and what I'd have to design for.

    So it looks like the only way to find what power switchmode regulator I need, is to buy the damn thing, put some batteries in it it, and take some current readings.
     
  4. daddles

    daddles

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    Jun 10, 2011
    Probably true... But I wouldn't worry too much -- you can find good regulated wall warts at a second-hand store for 50 cents to $1. I'd look for a 6 volt unit with good regulation (you'll have to buy it on speculation) or get a 9 volt unit and use a regulator to knock it down to a nice 6 volts.
     
  5. AYabroudy

    AYabroudy

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    Jul 28, 2012
    Have you had any success?

    Hi Heimhenge,

    Were you able to successfully create a power supply for the Rat Zapper? I'm trying to do the same thing and haven't had any success.

    I used a wall transformer that put out 6.5VDC at 300mA and another that put out 5.5VDC at 2000mA. With either of these power supplies I get no lights on the Rat Zapper.
     
  6. Heimhenge

    Heimhenge

    13
    1
    Jul 12, 2011
    No, I never got to that power supply experiment. I found the access point where the rodents were getting into my attic and blocked it. Haven't had a need to buy the RatZapper since. But if you do find a power supply that does the trick, please post your results in this thread. Good luck! I hate rodents!
     
  7. CDRIVE

    CDRIVE Hauling 10' pipe on a Trek Shift3

    4,960
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    May 8, 2012
    Look in the bright side. Arizona doesn't have Nutria. They get big enough to throw a saddle on! :D
     
    Martaine2005 likes this.
  8. Slick

    Slick

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    Jul 27, 2013
    Rat Zapper on 110 volt supply

    I want you to be aware of the fact that the rat zapper with the 4 D cells not only runs on the 6 vdc from the batteries, but there is a 3 vdc tap between the second and third batteries. There is a wire that runs under the plastic housing and is taped at the 3 vdc point. I bought a 110 ac to 6 vdc plug in power supply from Jameco Electronics for about $17.00. It's good for 3 amp. I discovered the 3 vdc tap when I was hooking up the power supply to it.The problem I'm having is getting a 3 vdc tap to supply the circuit. There is a small female jack on the top of the unit, which I assume is for testing at the factory. It only has two wires connected to it. I'm not sure though.If I find out just how it works, I'll post it.
     
  9. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,411
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    Jan 21, 2010
    Based on it having a 3V tap, I would suggest that the inverter (the part which generates the high voltage) uses a +/- 3V supply. In some respects this makes the design easier.

    This means that it would likely be drawing current from one 3V side then the other -- and probably substantial currents after a discharge -- so the current through the "centre rail" would be in both directions and probably quite substantial.

    Because it has to both sink and source current, a simple voltage regulator could not be used. In addition, and circuit capable of generating a centre rail would likely double the power requirements.
     
  10. Joe Gorin

    Joe Gorin

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    0
    Sep 15, 2015
    I have purchased the Rat Zapper UItra. I have questions and comments.

    It seems straightforward to use two 3V wall wart power supplies to power the unit, instead of the complexity of using a 6V supply and building a 3V tap that can both source and sink current. I have ordered the materials for this.

    Regarding this text, "There is a small female jack on the top of the unit, which I assume is for testing at the factory." My understanding is that this if for connecting the remote LED option.

    My plans are to connect a signal from this jack to a comparator/monostable that then powers a 12V circuit that runs a "mail chime" product. That way, I can be informed inside the living region of my house when a rodent is zapped, whether it happens a day or a year after installation. Long periods of duty are reasonable using dry bait (dog food).

    So my plans have three wall warts. Inelegant, but simple. Probably more reliable than using cheap modules to boost from a low voltage supply or buck from a 12V supply.

    Does anyone have any ideas as to how I should test the functioning of the unit, i.e. an artificial mouse?
     
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,411
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    Jan 21, 2010
    I would recommend that you test the device with a dead short across the zapper terminals. Measure the max current from the batteries and ensure your plugpacks are capable of at least that current.
     
  12. Joe Gorin

    Joe Gorin

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    0
    Sep 15, 2015
    I have learned some things so far:

    1. Testing. There is a page on how to test from an obsolete but similar product. As *steve* suggests, it involves shorting from the high voltage plate to grounded metal. Then you should raise the shorting element (screwdriver shaft) 3 to 6 mm above the plate. See the details here: http://www.derwenttraders.com.au/_l...nstructions_for_the_Raticator_Plus_rat_zapper
    2. Center tapped battery stack. The version I just purchased here in 2015 has no connections to the electronics except the positive and negative terminal of the battery of four cells in series. So my plan for dual 3V power supplies based on the observations by "slick" in 2013 is unnecessary; a 6V supply will work adequately.
    3. The connector is a 2.5 mm phone jack. Its outer conductor is connected to the negative battery terminal.
     
  13. Joe Gorin

    Joe Gorin

    4
    0
    Sep 15, 2015
    More learnings:
    1. The connector was 3.5 mm, not 2.5. It is connected to an open collector NPN transistor that turns on for a very short time when a zapping has occurred.
    2. I found that the "Rodent Zapper," a more modern and expensive product, has better usability due to its mechanical design with a top and bottom that can be separated. Cleaning the bottom is sometimes required.
    3. The Rodent Zapper comes with a plug-in power supply. And its output port was easy to interface to the mail chime.
    4. The first 40 days of service I caught no rodents. Recently, I caught one every night for four straight nights. I read, and it matches my experience, that it is critical to never handle the product with naked hands. Once you do, you should clean the lower part by soaking in hot soapy water for an hour; I also cleaned the upper part with alcohol. Then I used gloves every time I needed to touch it.
    5. Peanut butter bait lasts for much longer than I expected. I saw no degradation in 40 days.
     
  14. ChosunOne

    ChosunOne

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    90
    Jun 20, 2010
    Just for anyone who would like to replace a 6VDC battery (such as 4 "D" cells) with a well regulated 6VDC plug-in power supply: I have a stash of old 6V DC power supply PCBs from the early 80's alarm industry--analog components, very reliable, that have been "mothballed" for ~30 years. Their default calibration is set at ~;6.8 VDC (designed to charge sealed lead-acid batteries), but can be adjusted by potentiometer to 6V. The PCB power input requires a 12VAC transformer, which I can supply. It comes in two sizes: 250mA maximum sustained output and 600mA max sustained output.

    Will supply higher outputs for brief periods (unspecified, but I have used them for up to half an hour at higher current). These power supply boards are designed for 24/7 operation, and overload protection is a self-resetting thermal breaker, not a fuse. Shorting the output will cause a "ping---ping---ping" sound of the breaker opening and resetting.

    These PCBs are among a ton (literally) of mothballed equipment that I'm committed to sell off this year. I will accept any reasonable offer that makes it worth my while to package it and take it down to the post office.
     
  15. TMH

    TMH

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    Jan 2, 2017
    I just converted a Rat Zapper Ultra with a 6v 2amp power supply. Green light came on so I put it out in garage. No way you would get 50 kills from a set of D cells. I maybe got 6-7 kills and would get blinking red light on reset. I also have some old Black and Decker VPX batteries that seem to power it up just fine also, still looking into that.
     
  16. Audioguru

    Audioguru

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    Sep 24, 2016
    Why would a mouse or rat live in a very hot attic?? It is not a lizard.
     
  17. TMH

    TMH

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    Jan 2, 2017
    It just took out a mouse and reset to green light with no problems, they love them cat treats! The traps haven't been out in garage for a while to figure out battery issues, but that was fast! Again, working trap on 6v 2amp power supply, cost of about $4.50 in supplies and a little time. Would add pic but seems a pain. On to mod the other two tomorrow, past my bedtime.
     
    Last edited: Jan 2, 2017
  18. Joe Gorin

    Joe Gorin

    4
    0
    Sep 15, 2015
    Because this thread is active again, let me report on my last year's experiences with AC-powered rodent electrocution devices.

    I continue to use the Rodent Zapper, which comes with AC capability. I continue to have it interfaced to the "Mailbox Chime" product, so it lights a resettable indicator in my bedroom when it triggers. I caught mice on five straight nights after thorough cleaning to remove human odors, and have then caught about ten more in the rest of a year. I now always wear gloves to prevent odor contamination.

    I got false indications twice in this year. I know that one cause of a false indication is a power interruption. I have been using either peanut butter or almond butter as bait, and neither has dried up to uselessness between events. I smear a tiny amount at the entrance to the trap, too; occasionally a rodent will take this bait and set off the trap without getting the main bait or getting zapped. But I always seem to catch one within two days of noticing such an event.

    I really like the idea of a trap that does not require active monitoring. There are some products on the market that have a wired remote indicator. That may work for many people, but I like the mailbox chime wireless remote instead of wiring the standard remote. Also, at least one company has a remote that is battery powered with a non-replaceable battery. That seems like a good way to have problems: When the batteries fail without your knowing, the last rodent killed will decay and the trap will stop working without informing you.
     
  19. TMH

    TMH

    4
    0
    Jan 2, 2017
    VPX batteries also work just fine.
     
  20. TMH

    TMH

    4
    0
    Jan 2, 2017
    Not monitoring means it tells you at any point.
     
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