Quid Pro Crow

Simple, inexpensive bird feeder that dispenses peanuts in exchange for dropping stuff in a hole. A vending machine for clever birds.

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An inexpensive, simple bird feeder that dispenses a nut for stuff and can be built from analog components and discarded objects. Rodent proof, runs on 5-6V, one moving part (vibration motor). No 3D printing or laser cutting required, just some basic hand tools. Lots of improvement and customization possibilities. Lots of possibilities for the enclosure.

- runs on 5-6V (4x1.5V cells, USB powerbank, 5 or 6V DC adapter)
- comes on when it sees a warm body, stays on until it's gone
- detects when something is dropped in the hole, anything that fits will work
- dispenses a shelled peanut (maybe two or three)
- dispenser design is rodent-proof
- can be built in a weekend
- no programming/all analog
- cheap to make
- small enough to be portable
- easy to customize
- easy to improve upon

I had been thinking about this project for a while and got really inspired by Hans Forsberg's videos and comments. I wanted to make a very simple version of what he's been doing. I also wanted it to be small, cheap, using common analog components and discarded items.

I wanted to avoid programming and 3D printing - not that I don't love that stuff, but to keep this mechanically and electrically simple, cheap and accessible.

I hope this can be the type of project you can build easily, try it out and improve on it over time.  There is a lot of room and possibilities for improvement and enhancement. Solar charging, cameras, computer vision, do it all with a microcontroller, print better parts, more efficient design... lots of room for improvement :)

I've already built a prototype and started testing it with birds that visit my balcony (mostly pigeons, but some jackdaws, crows and magpies). The vibration motor does not startle them - especially when they learn it means a peanut is coming,

The circuit is fairly straightforward:

  • PIR sensor (the one thing I could not find laying around and had to buy. This turns on the rest of the circuit when triggered.
  • 555 monostable vibrator to keep the circuit on for ~30 secs after the PIR is triggered. There is a diode leading from pin 6/7 to the trigger. This allows the PIR to reset the timer during a cycle, keeping the thing continuously on while a bird is in front of the PIR.
  • LM358 dual op amp for the IR proximity sensors made from IR leds and phototransistors
  • another 555 for a bistable vibrator - when the drop sensor sees something it turns the vibration motor on, when the dispense sensor sees something it turns it back off
  • a third 555 astable vibrator - to use as an optional timed dispense to get birds used to it as a food source
  • small DC motor (the one I used is marked 2 volts) with a slice of cork pressed on the axle and some screws in one side of the cork to make it vibrate
  • some resistors, capacitors, a few transistors and diodes and signal LEDs to indicate what's going on

The circuit was the simple part.

Biggest problem I had to solve was dispensing one (or maybe two) peanuts at a time reliably without a complex mechanism or making peanut butter. A vibration feeder made from two jar lids with offset holes finally did the trick. This was a challenging puzzle to solve. I probably spent most of the project time on this.

The next one was sunlight - some leaks and reflections were triggering the sensors. Some foil tape and a better enclosure fixed this.

One interesting thing I discovered was that black shrink tubing did not trigger the IR proximity sensors, making it a great material to use as a backstop, letting you turn up the sensitivity a bit without extending the range - great for monitoring openings and chutes for passing objects.



Only the PIR and the FEEDER ON/OFF (monostable vibrator) are on until the PIR is triggered.

If it's in timer mode, the TIMER (astable vibrator) is also on.


  1. PIR sensor triggers monostable vibrator
  2. 555 Monostable vibrator turns on rest of circuit via an NPN transistor and keeps it on for ~30 sec after the last PIR trigger


  1. Deposit sensor detects passing object and triggers op amp 1
  2. Op amp 1 triggers bistable vibrator to go high
  3. Bistable vibrator turns on vibration motor via an NPN transistor


  1. Dispense sensor detects a passing peanut and triggers op amp 2
  2. Op amp 2 triggers bistable vibrator to go low
  3. Bistable vibrator turns off vibration motor via an NPN transistor

Timer Mode

The above is still true, but in addition:

  1. 555 astable vibrator completes ~50 min cycle and its output goes high to trigger
    1. NPN transistor to turn on the sensors and motor switch
    2. NPN transistor to turn on the motor
  2. Dispense cycle triggered as described above

The schematics in the project description should be readable. It's broken into modules, but the interconnections are labelled.

  • For the monostable, bistable...
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Pigeon takes bottlecaps from the bottlecap magazine and sinks a couple.

MPEG-4 Video - 2.38 MB - 10/25/2022 at 20:14



Basic functional test of the new stripboard pcb with sensors and motor attached.

MPEG-4 Video - 43.53 MB - 09/16/2022 at 18:49



Shows the bridges and cuts used for my stripboard-mounted circuit.

Portable Network Graphics (PNG) - 323.24 kB - 09/16/2022 at 15:27



Schematics showing the different parts of the feeder electronics.

image/png - 123.65 kB - 07/20/2022 at 20:55


Nerdfeeder 1_10-29-36.mp4

The jackdaw family has taken notice.

MPEG-4 Video - 4.76 MB - 06/30/2022 at 10:12


View all 14 files

  • 1 × PIR sensor Small PIR sensor with short (1-3m) or adjustable range
  • 3 × NE555 Timer
  • 1 × LM358 Dual Op-Amp
  • 1 × Small DC Motor
  • 1 × Wine cork, eraser, test tube stopper or something like it to make a push-on load for the motor

View all 37 components

  • Upcoming Changes - Failure Modes and Inefficiencies

    Stephen Chasey01/19/2023 at 11:38 0 comments

    I've had some time to do some testing and will make the following improvements to the control circuit. I'm going to hack these into the current PCB, so it will be messy. If it works as expected over time, I'll make another layout takeing these changes into account.

    Failure Modes

    • Power drops below 4.5 volts for the motor control 555 - can cause the feeder to miss deposited objects
    • Deposit trigger may get jammed and cause the dispenser to run contantly
    • Dispense trigger may fail to respond or the hopper is empty, causing the dispenser to run contantly


    • Powerbank Keep Alive always running, even when the feeder draws enough power to keep a power bank on.


    • Power - Will only switch power to the sensor LEDs and phototransistors
      • Motor control 555 will not suffer from a voltage drop below 4.5 volts as it does now
      • Standby current usage will increase, but still be under 50mA
      • Can reliably use a 5V USB charger or power bank again
    • Deposit Trigger
      • Will add a couple resistors, a cap and a diode to keep the trigger pulse short, even if the sensor is constantly on. 
      • If the deposit chute gets jammed or very dirty the sensor may cause the motor to keep running and dispensing peanuts. 
      • This will partially mitigtae this failure mode - if the sensor is jammed it will still start up the next time a bird triggers the PIR, but will stop the dispense motor from running indefinitely.
    • Dispense Trigger
      • Will turn the bistable 555 controlling the motor to a monostable with a period of ~20 sec. 
      • If the dispense sensor does not trigger for some reason within that time, the dispense motor will stop.
    • Powerbank Keep Alive
      • Put a 10K resistor between 555 pin 4 and the power rail so I can add an NPN switch to turn off the keep-alive pulses while the sensors are on (they draw enough power)

    I should have these changes in place before the weekend. I'm eager to get the feeder back up and running.  Once it's working I'll need to update the description, components and schematics. A new PCB layout will come shortly after everything is confirmed.

  • Back on it

    Stephen Chasey01/13/2023 at 13:41 0 comments

    Holidays are over and things are back to normal, so I'm starting to get the feeder ready to remount on the balcony.

    After some multimeter diagnostics, my current design will run at 5V, but not reliably. The voltage drop across the BD139 puts the sensor's 555 in questionable territory voltage-wise, and I think it occasionally misses triggers from the deposit sensor due to this. I could replace it with a CMOS 555 and that would probably sort it out. I have a few laying around. The LM538 op amp runs at 3+ volts and the CMOS 555 from 2+ volts. After some PCB surgery and multimetering I found that the voltage with both sensors on and the motor running can go as low as 3.5 volts. Still, this should be ok if I use a TLC or LMC 555.

    I tried to make a PNP-based switch for the power-bank keep-alive power rail, but that didn't pan out. The way I put the PCB together makes it difficult to hold the keep-alive 555 in reset while the feeder is on. I would need to do some more PCB surgery to fix this. Then I could just use a BC547 and a 10K resistor to ground that pin when the sensor power rail is on. However, Isince I'm running off mains right now and it looks like I need 6 volts for the time being, so ths will probably have to wait for the next PCB version in a couple of weeks.

    I experimented with putting this all on a PIC, and it would be pretty simple. Any uC with 8+ pins and a couple of ADC channels would work. Also looked at some ESP8266 and ESP32 modules with a PIR and camera built-in, which could also handle everything in addition to replacing the RPi I'm using as a remote camera - but they are not that easy to find for me. I tried using pulsed IR to reduce ambient light issues. I experimented with this a bit on the PIC, but for proximity sensing I could not get it to work as well as the current version.

    Before I go digital with this I want to make a solid analog design that runs for a week on a 10K mAh 5V power bank, and what I have now is still pretty far from that.

    While I work on all these problems and experiments I'm just going to put the current PCB back in the feeder on 6 or 7 volts so can keep working with the birds.


    I finally thought of the obvious solution after writing this. Just control the voltage to the sensors themselves (just the leds and phototransistors), not the 555 and op amp. I'll use a but more power in standby (~50mA over 20mA), but should be much more reliable and let me use a 5V supply with a few modifications to the current pcb.

  • New Project Name

    Stephen Chasey11/13/2022 at 21:41 0 comments

    First I want to thank those who provided suggestions when I asked a while back. They were excellent and got me thinking. I have spent a little time every day since then thinking about it.

    Not sure Quid Pro Crow (meant to mean "something for a crow") is much better than Nerdfeeder, but at least people won't think it's a feeder for socially awkward humans any more. They will probably just think that I am a socially awkward human with a corny sense of humor - and that would be much more accurate :)

  • Could use some help

    Stephen Chasey11/10/2022 at 17:05 0 comments

    I would like to polish up this project enough to share plans and training guidance so others can build and experiment with it.  I already got some great feedback for better names for the project, but haven't settled on anything yet.

    The feeders built by Hans Forsberg and the Morsings are great, but require a lot of space and my guess is they cost well over 100 EUR for components and materials.

    The Crowbox is already available as a kit, but also costs well over 100 EUR to get parts cut and for components. The plexiglass alone costs over 100 EUR.

    The Crowkit seems to be more or less abandoned, though there are sometimes kits available. However people seem to be price gouging on these. The auger dispenser is also reportedly not very reliable. Kits including just some 3D printed parts and a handful of analog components cost 100 EUR or more:

    The designs I've shown here can be built for 50-70 EUR including the enclosure if you have to buy the whole BOM (nothing already lying around your workshop). The dispenser could be slightly improved as it occasionally (1 in 20 dispenses) does not dispense a peanut (just a crumb sometimes) and sometimes (1 in 10) the peanut takes 5-7 seconds to come out.

    I had been holding off on this since I'm primarily getting pigeons and wanted more examples with corvids, but the pigeons are showing promise. Switching from peanuts to cat or dog kibble would probably solve this problem (pigeons don't like it as much as peanuts but corvids like it) and I will give that a try when I return to NL next month.

    Anyway - if there is anyone out there that is interested in collaborating with me on this, I am eager to make this project available and accessible so people interested in experimenting have a lower-cost alternative to the existing solutions, and with easier to source components. SBCs are still hard to get and expensive these days. Also I may be tunnel-visioning here and could use some fresh ideas :)

  • Some Things I've Learned So Far

    Stephen Chasey10/31/2022 at 18:20 0 comments

    I'm heading to my hometown for a month, and while I want to leave the feeder up while I'm gone, I don't think it's ready for that just yet. There are some tweaks I need to make to the PCB and the sensors to make it more reliable and I don't feel good about leaving it unattended for so long since I've only had V3 up for a few weeks so far. 


    Building analog helped me better understand what's happening and breadboarding made things easy to adjust. While my next step will be to use a microcontroller (likely a PIC16F1709) I think this was a good step for me to take. It forced me to keep things simple and not get too distracted by "nice-to-haves".

    This also helped me focus on solvng problems I have rather than try to solve too many future problems. The Morsings spent some time coding up a CV object differentiator to tell trash from natural debris and found they did not need it. To me this is somethings you would do if the birds were putting pebbles, twigs and other non-litter bits in the feeder, not before they have brought you anything at all. What they did is impressive, but I only want to make what I need and don't really have the time or resources to go down any rabbit holes.


    My current circuit and motor use about 850mA when the feeder is dispensing (max power consumption). It can be run by anything tha can supply 5-6 volts and 1 amp. Since the feeder is only activated when the PIR sensor is triggered, idle power consumption when no birds are present is probably around 20mA (not including the optional keep-alive pulse of ~150mA).

    One improvement I will try to work into the existing PCB is for the powerbank keep-alive to only work while the feeder is in idle mode.

    I originally designed this around 6V and think that since moving to 5V the drop sensor, which draws about 200mA with 4 IR LEDs, has become a little unreliable. I'm not sure what it is. I probably need to put slightly higher value resistors  on the IR LEDs (each has a 100Ω resistor connecting it to ground) since the actiual voltage going into them is closer to 4.5V due to transistor forward voltage. Some more testing and tweaking is required here.


    Vibration dispensors worked best for me. Augers are ok if you are using a strong motor like a drill and don't mind wildly variable amounts dispensed, crushing the food as you dispense, and eventually turning things like peanuts into peanut butter. Hans Forsberg uses a 3D-printed vibration dispenser and the Morsings use a drill/auger setup. Since I am building small and low-power I used a very simple vibration dispenser I came up with (that certainly has been done before - but I have not yet seen examples) and can build out of jar lids or PVC end-caps.


    The enclosure should be durable, light-tight, stand up to the weather and allow for access to the electronics. It's also nice if you can mount it on something to keep it off the ground and away from non-avians. My latest version is made of PVC pipe and is working great, but I miss the ability to access the insides easily like I could with the first two models. Not so important once you dial everything in, but being able to tweak things without disassembly is great while you are tweaking and experimenting.


    I have been using shelled peanuts, but the problem with these is that almost all birds love them - especially pigeons. You could also use small cat or dog food, which corvids like but pigeons can't eat easily. I have thought about using peanuts in the shell for the same reason, but that will require a scale-up of the dispense mechanism and more testing - I'll get there.

    Peanuts and cat/dog food will contain small crumbs. I had some issues with the feeder dispensing a tiny particle of peanut or peanut skin, apparently not dispensing anything to the birds. The dispense sensor would see something go by and turn off the dispenser. One of the reasons I tuned the sensors - now it's less likely to...

    Read more »

  • Bottlecap Magazine

    Stephen Chasey10/25/2022 at 20:38 0 comments

    I left the feeder unattended in timer mode for 3 days, then switched it to normal mode. The gang of four pigeons that frequented the V2 feeder have dominated the V3 feeder. Unfortunately they have become pretty territorial. A couple of them seem to remember the old feeder and picked it up again quickly. 

    Since I'm stuck with them for now I want to see how far I can get with them while I figure out how to fix the situation.

    Instead just of leaving bottlecaps and butts on the platform to train them, I put them in a 50mm pvc pipe with a cap and a bit cut away so caps can come out. They jam a bit and have to be pulled out. I was thinking this is one step closer to getting them to bring a cap from elsewhere. Within an hour they were pulling out caps and getting a few in the hole.

    I added a short video to the file section:

    Putting the caps in a pipe like this not only makes the birds work a little more deliberately once they start to understand there is a connection between the caps/butts and getting food. I put about 20 caps in and the pigeons emptied it 4 times today.

  • Cameras Online

    Stephen Chasey10/21/2022 at 14:31 0 comments

    My two RPi cams are up and running now. I have motion detection on to record on the wide-angle cam attached to the feeder. The other one attached to the door (inside a PVC shell) has some people's balconies in view so I don't record with it. I need to find a better place to put that one.

  • Version 3 Deployed

    Stephen Chasey10/19/2022 at 15:09 0 comments

    I finally finished putting the PVC version together. I really miss the sliding panel on the wine box - things are not very accessible now. However it is more weatherproof, holds more peanuts and loads from the top :). Camera angles are more limited now that people are moving into the new apartments across the street - I don't want to invade their privacy. It's powered by a 5V phone charger.

    It seems to work about as well as the wine box version (V2). I may have to tweak the dispenser a bit more, but so far it's reliable. I'm also adding a second camera using a Raspberry Pi I bought about 10 years ago - it doesn't even have mounting holes in the PCB. I need a PVC end cap to complete my enclosre for this so it will be up tomorrow.

    Pigeons are already poking at it today, but it will take a week or so for the jackdaws and magpies to trust it.

    I think V4 will need to have a properly designed enclosure - I love building things out of found materials, but after 3 versions built from discarded items I think I'm ready to really optimize it. I'm visiting my hometown soon and will have access to woodworking tools and a friend's 3D printer. I just know this can be made smaller, easier to access the internals, and easier to mount. 

  • Rename?

    Stephen Chasey09/19/2022 at 14:56 5 comments

    It looks like my project name could use some improvement. There are a lot of things and people out there already using "nerdfeeder" and the resulting confusion is understandable.

    I was thinking more along the lines of a birdfeeder for nerds - or maybe that the birds themselves must be nerds if they can figure this out. Mostly, I liked that it sounded like "birdfeeder".

    I haven't been able to come up with a better name yet, other than a few that could be equally confusing, like "Nuts for Butts". 

    I'll be thinking, but if anyone reading this has a clever idea I would appreciate any suggestions.

  • Stripboards tested and schematics updated

    Stephen Chasey09/16/2022 at 15:34 0 comments

    Everything seems to work on the new boards, so I updated the schematics and stripboard diagram.

    Stripboard PCBs


    Cuts and Bridges

View all 46 project logs

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John Opsahl wrote 09/23/2022 at 04:35 point

This project is way cool. Do you have a video of a bird dispensing an item and receiving a peanut? 

  Are you sure? yes | no

Stephen Chasey wrote 10/19/2022 at 14:52 point

Yes, there are a couple of videos in the files section.

  Are you sure? yes | no

Stephen Chasey wrote 08/07/2022 at 06:58 point

It could be adapted to dispense a peanut for each commit :)

  Are you sure? yes | no

fdufnews wrote 08/05/2022 at 14:22 point


When I read the title, I first thought of a system to feed a pool of programmers

  Are you sure? yes | no

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