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I saw this unit in a local farm store (Farmers Combine in Ramsey) and bought it for us to explore.
It's more or less an automatic air freshener unit with a can of fly spray, but it seems to be an older design similar to the units used in commercial restroom facilities.
I think the chip is a dedicated ASIC (Application Specific Integrated Circuit) that is specifically designed for units like these. It seems to have integrated timing modules with internal capacitors, and has an extremely low quiescent current measured in microamps.
The spray is 1% pyrethrin with Piperonyl Butoxide, a chemical that makes the pyrethrin more effective by reducing insect defense against it. Pyrethrins are based on a natural defence chemical generated by chrysanthemum plants.
Most home sprays are about 0.1% pyrethrin here. But also get sprayed a lot longer.
The unit is very hackable for custom use. There are two distinct timing modules which are set with external resistors. One controls the motor run-time and the other sets the timing clock which determines the time between sprays. The LED flash timing is also derived from that clock, so shorter delays result in faster flashing.
A totally custom time between sprays could be set with a 10 Megohm potentiometer in series with a 240K resistor to set the minimum time and allow variation up to a few hours between sprays. That could be useful for very light scenting with a fragrance spray.
In hindsight, I'm thinking that the two connections for the time setting resistor may indicate that it is effectively across an inverter with an integrated capacitor on the input to create a simple oscillator.
The use of a metal grip for the top of the can means that the unit can accommodate non standard cans, or with a slight modification to the case it could take full size unmetered cans.
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One of the interesting things about living on an island that is a very strong agricultural industry is that they have shops that are just dedicated to supplying the farmers and one of those local shops is the farmers combine, and i took a look in today and i Saw this this is an old device, it's been sitting the shelf for a very long time. The box was not looking very clean and the thing was black inside, but i bought x. I thought it was interesting and those of you familiar with the air fresheners will see that this is like a public toilet air freshener, but with the light sensor, as opposed to the home version, which doesn't have the light sensor and they've simply put a can of You know dosing uh insecticide in it instead, and this contains one percent parathyroids, which is a it's that natural insect repellent derived from chrysanthems or or synthesized from that technology. But it also says synergized by piperonobutoxide.

That's quite interesting! It's all right because piperambutoxide doesn't actually kill insects, but it stops themselves defending them against the pyrotherm, which makes it much more effective for a smaller dose. It just increases efficiency. This thing is so old that it's even got the original uh duracells, which the date on them the expiry date is 2019, so they expired two years ago. But it's got that thing that you press this tab and you press this tab and after a while, you see a little bar go up the side, it's that sort of thermally active thing and it shows that they've only got about half their capacity left.

Let's actually get a knife and slit into one of those and i'll show you that's basically speaking uh that liquid crystal encapsulate liquid crystal it changes color depending the temperature and inside this i expect to see just a conductive strip that is pressed against the battery contacts. Let's see if we can get this off intact, oh am i going to get this often tight, maybe not hold on. I should do my best, even if it means pausing. Oh it's stuck on.

That's not very good right. That's a bit messy, but not to worry. I shall persist so it's kind of stuck on. Oh there's the strip there's the strip, so what we have here is - let me just get this down on the back of this there's: a metal contact and they've, basically printed conductive ink in the back of that, and it folds around the end where i've just broken It off and when you press that across current flows, but because it's tapered, it means that it warms up, but the harder.

The current, the initially the low end will get hot first. So it will show the color, but it takes full current of a fully charged cell to actually make the the wider end hot, which then uh shows the good charge in the process. It probably takes quite a bit of current uh to actually do that, i'm guessing it draws a. It will draw quite a lot of current to actually heat that up, particularly given it's pressed against the cell, so uh not great.

It was a novelty. Sometimes you got cells that that had been squished in postage or shipping or storage, and the cell was completely flat as a result of basically being in permanent, self-test and drain the cell. They don't do that these days. Let's take a look at this.

I shall zoom back out because we need some more room, so this thing once opened up. I've put new batteries in it very stylish purple. It's got a switch here for the light sensor here. Uh, it's got the option of 24 hour.

It will just run 24. 7, it will just keep dosing throughout the day and night and it's also got the option of night and day. So if say, for instance, the insects were only active during the day, you could actually switch it to that and when it detected the light it would actually operate um and if you switch it to say, for instance, you want to only operate at night. You could actually make it soap and it detected.

It was dark, it would operate, but then it's also got this little switch five minute, 10 minute, 15 minute and 30 minute settings. Let me put the kind of spray in interesting to note and it's quite a nice feature. It uses a metal lip here to actually support the can and it means that cans of different sizes can be used. I'm just going to push that thing up, because it's one of these spring-loaded return ones.

I want to make sure this goes in all right, but because that grips the metal rim here, the can doesn't actually hit the bottom of the the case, so it can effectively use a wide range of cans. Presumably, although i've only ever seen the insecticide in this version and then when you turn it on, it will immediately activate. I shall point it away from you i'll put that up to the 24 hour mode and then you'll see it push down that nose. Little spray.

A portion of insecticide roughly in the direction of my face: oh there, it goes that was not sitting right hold on there's two versions commonly found of these. Some uh run the motor in both directions to actually wind that back and the others just rely on the uh, the springiness of the can actually returning. Let's try that again there we go and each time you turn it on. It immediately gives out a dose which isn't a good thing, because uh when the battery runs low in some of these type of devices, every time it triggers and pumps, the voltage drops and it resets the processor and then it so it does a dose of spray.

Then the processor resets and then it immediately sprays again they can go into a loop cycle of spring continually. I don't know if that affects this one or not, but we've seen that operator, i'm not going to spray any more insecticide into the air in my vicinity. Let's get a screwdriver and pop the lid off, let's just pop this base off this thing was so black. It had done that thing where it had been electrostatically just accumulating smooth from the air just dirt.

It was black and interestingly, this area around here. It basically electrostatically precipitated all around the inside of this. It was quite interesting. Let's pop the cover off the commercial ones used in public restrooms toilets, sometimes had big d cells in them they were designed to last a very long time between refills.

This is a just using the double a cells, so i guess new batteries each time right. What we have here is the actuator mechanism, it's nice, that, instead of all falling to bits, it's actually everything is pinned together onto that there's a fairly standard motor in the back here, little dc, motor and uh. It winds onto this cog then reduces down to that cog, and then it winds onto the edge of this uh cog here and that's the bit that pushes down on the can to actually do the spring. But it does rely.

It only runs in one direction and relies on the springiness to push it back up again. Quite often, you'll find that if these units have operated without a can, that thing is wound down to its full limit. You actually have to push that up with something uh to get the cannon like i did earlier on. Let's take the circuit board out.

Oh it's worth mentioning, there's a separate switch down here to kill power to this unit up here. That's quite unusual. I thought they might have put that on the circuit board, so this is two screws. Is there anything going to fall off when i take this out? No, it's not cut.

It's not getting. Little covers over the switches. So what do we have just the switches in the capacitor in the front, an led and photo sensor? There's a transistor that switches the motor gas, a chip. Where is my magnifying glass? The chips number is the hr.

8012. Hr8012Cn. Don't know i don't know. If that's a custom chip or not, i shall investigate it right.

Tell you what i'm going to do? The usual reverse engineering and i'll be back in a moment, and we can take a look at this circuit board. Okay, let's explore. Incidentally, i tried the little uh battery monitor thing. I peeled the label off carefully off the other one, and i tried across the bench purse plate 1.5 volts.

It passed 300 milliamps, i didn't realize initially the little cardboard strip at the back was for thermal isolation from the case. Just for the area of the indicator. Strip 300 milliamps isn't actually too bad. Here is the front of the circuit board, shown the correct way around and there's the switch for uh selecting the different time settings.

There's a transistor that drives the motor we've got a red led, marked g and we get the photo sensor, possibly a photo transistor and the three position switch for the times and a little smoothing capacitor across the power supply rails. I think the date this might indicate 90s and that so that might be 1993. That would probably sound about right, not sure could be wrong, but um. Let's take a look at the other side of the circuit board.

I shall brighten this up. Just a tiny little bit, we have this dedicated chip and don't know if this is a microcontroller or a dedicated chip. Purely to this task, it's called an hr 8012 cn a search for that in google brought up absolutely zero, which is very unusual. The only things notable here that are really particularly unique to this device and i'll show you the rest in the circuitry but notice how they've actually set the time by a resistor here, but there's actually eight resistor positions.

However, there's only four actual resistance values: they've got them paired up, so they can stack two resistors in parallel to fine-tune the value to get an accurate time as it is. They used high precision resistors with a complicated alpha, numeric code, so uh that results in odd values like 499 k or 768k 240k, which is a standard value and 1.5 mm, which is a high value. And what else is there to say here? There's not much else to say at all right tell you what let's bring in the notepad. I shall tame this down as i bring this in, because it's going to be quite bright.

Otherwise, let's zoom in here are the two batteries, the double a batteries and they go onto the circuitry via the switch. We've got the three volt rail from the batteries and we've got the zero volt rail. The time it's quite unusual. The time setting is the switch that switches between these resistors, but also the switch itself is only powered when the actual device wants to actually so possibly a microcontroller when it wants to actually measure the time setting it powers this up and measures the resistance coming back.

It must be using some internal divider or something like that - really not sure it does have this 240k resistor externally, not sure again what that's for, if that's associated with this, it might be some internal op amp. Technically speaking, i could have actually tested that by bridging that out and see if it changed the speed of the flashing led. I may do that. If i do it, i shall leave a comment in the description down below there's the flashing led itself.

It's connected straight between the output and the zero volt rail, which suggests that this is a possible dedicated chip, because normally you wouldn't just connect an led to the output of a microcontroller pin. The photo transistor is quite odd because it also is only activated when they want to read that this must be to save battery energy, but to activate that this pin here is taken positive and then that resistor and the photo transistor form a potential divider. With the current, through the transistor, depending on the actual light level, and then that is read by this pin so two pins to measure the light level and two pins to measure the resistance, the night day and 24 hour switch, is simply a three position. Switch that simply grounds uh, one of these pins to the zero volt realm on the output, we've got a 1.2 k, resistor feeding the transistor, which is an ss805 oh 1.5 amp, 25 volt gain of somewhere in the region of about 100 to 200, and that drives The motor which uh pushes the plunger down and it has a little capacitor across it just for decoupling, and that is it there's it's basically speaking, it's a textbook circuit for this type of thing, all right tell you what i'm going to do that test right now.

I'm not going to leave the comment down description, i'm just going to well. I probably will, but i'm going to do that test right now and see if that resistor shunting it with my finger or another resistor will vary the speed of the led one moment. Please experiments have been done and i'm very glad i did those experiments, because i've discovered some interesting things. Let's get a bit closer to this.

The unit is happily pulsing away. Watch this. This is the actuator arm uh running down to push the can watch the duration of the running, so i turn it off and on again and it runs, it has a sort of overrun time. So that's the duration that it's going to press the.

Can i put a resistor across this resistor which appears to set the timing of that. So, if i bring this in, this is a 10k resistor. I've got it set at. If i put that in parallel with that resistor - and i turn this off and on again now watch what happens to motor, it just gave it a wee, tiny burst and if i turn it off and again, each time operates.

It's just a tiny burst so that resistor specifically sets that duration. The timing resistors, i experimented with different values so turn this on and if you notice that timing is based depending on the choice of resistor here, it seems to affect the whole time the circuit, including the speed of flashes. If i put my finger across the back of this you'll see the led going a bit berserk and flickering and flashing, because it's quite easy to change that, and i tried i replaced the five minute timing resistor, which was the lowest value one. What was that one? That was a 240k.

I replaced it with 3.3 mega ohm and it changed the time to roughly one hour. Eight flashes per minute, 4.7 mega ohm changed it to five flashes per minute, so roughly 1.5 hours and 10 mega, which is the maximum i'd recommend going. But, to be honest, i'm not sure how stable it'll be with that uh slowed it down to just three flashes a minute and which would equate to roughly about 2.5 hours between operation. So it is hackable.

You can fine tune things for the duration of the press. Um and also the the timing itself, the duration between the presses. So that's quite interesting, it's nice that it's all adjustable. I think it does hint that that is a dedicated chip.

I wonder who makes it? Is it a whole texture, not really sure? No, i don't think it is uh because they that number the ht it starts hr, not sure yeah, that's very interesting. So this is what it's like inside a farm uh industry insect spray unit. It's used in like dairy cattle, uh barns and chicken burns and stuff. Like that just to either kill the insects or just basically create a less favorable atmosphere for them in that area to protect the animals so very interesting, well worth taking apart.


10 thoughts on “Farm-grade automatic insect spray”
  1. Avataaar/Circle Created with python_avatars City Lights says:

    Thank you Clive! You just solved an issue I have in my 10×10' grow room. I've been using the Glade Air Freshener version of this dispenser, with the North American version of the insecticide spray called Doktor Doom to treat Thrips in the grow room. Currently it's max time is 36 minutes witch is to often for maintenance insect control. Now I'm going to add a variable pot and will only need a can and a bit per year, instead of over 3 cans a year 🙂

  2. Avataaar/Circle Created with python_avatars Chris Bleurgh says:

    So I see the batteries in the unit and think "Dang, when was the last time I saw those built-in testers for disposable batteries" and got sucked into a short lived rabbit hole on what they were and where they went. Realizing I'd disassociated from the video, flicked back to find him explaining the last bit of info on the bloody things before he moved on. How dare he make a mockery of my attention span.

  3. Avataaar/Circle Created with python_avatars David Evens says:

    Here in North America, there's a chain called Tractor Supply Store (Peavymart in at least part of Canada now) that started out as farm supply, and still has things like electric fencing materials and equipment that you don't find in most similar stores, but it's moved a bit into the more general merchandise with an emphasis on farm products. So, they have clothing, but it's the kind of clothing you need for farming, like heavy coats, raincoats, rubber boots, and various sorts of work gloves. They also have things like welding machines and a much broader range of air compressors than more general large hardware stores like Canadian Tire carry.

  4. Avataaar/Circle Created with python_avatars Hola! Dave Bell says:

    What makes me hesitate is that not all farm insecticides are authorised for domestic use. But my personal experience is old and in England.

    There's nothing about the chemistry that sounds immediate alarms but the whole feel is a bit like giving Gordon Ramsay DIY instructions on installing 3-phase power in his kitchen.

  5. Avataaar/Circle Created with python_avatars Andrew Radford says:

    Years ago my stepson and his marine biologist wife were renovating, and they removed all the insect screens in their house. Due to all the mosquitos she placed a similar unit right above where their baby slept. When I noticed this I asked my partner to have a gentle word with her and suggest a mosquito net.

  6. Avataaar/Circle Created with python_avatars coondogtheman1234 says:

    I have a board from a singing greeting card and when I put a finger on one of the resistors it makes the music speed up. I can do the same thing on this toy audio recorder which uses the same chip as used in the Yak Bak recording toys back in the 90s if I wet my finger and put it on a resistor and ground it makes the recording chip record at a faster rate so if you record while doing this it records in better audio quality but less time. I am trying to find something like a small pot to install on it so I can warp audio.

  7. Avataaar/Circle Created with python_avatars Pat O Mahony says:

    Nice tear down. Been musing since I posted a comment on one of other comments. Problem with using this in a fanny flambeau project is these spray cans give a metered dose and shut off at end of stroke. So solution mod a canister by fitting a refill valve. Schrader or presto tyre valve soldered in to side of can or a valve from a refillable lighter. This gives a measured dose of gas. Next a combustion chamber behind nostrils with a spark igniter that kicks in just as plunger cuts off gas supply. Nice project to experiment once you don’t create work for IOM rescue services in the process.

  8. Avataaar/Circle Created with python_avatars Gazr Gazr says:

    Looking at the battery checker strips using current to warm up indicator,
    Similar thing I have a Nokia phone, that just does texts or you can actually ring someone up and have a conversation, daft thing is when battery is running low , it beeps every so often but also lights up the display screen to show you this, so further current draw is wasted, this progressively gets to shorter intervals so flattening the battery even quicker 😎
    Gaz North Yorkshire.

  9. Avataaar/Circle Created with python_avatars Ian Butler says:

    I have a Thermcell mosquito repelling unit that heats a pad with butane that contains that substance. I live in the Ohio woods near water, and it is quite effective to use. I have a small one for hiking and camping and it is also quite good. I think the US military issues them, which generally means they work.

  10. Avataaar/Circle Created with python_avatars john morgan says:

    I'm imagining Clive, with little storage boxes full of components salvaged from products, such as small plastic gears, PCB's, switches etc. for his own little projects or repairs.
    I'm seeing a active Christmas tree in the Department of Villainy's future, with whirligigs and disco ball baubles.

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