I haven't tried this, but "under 15 euros" seems a little optimistic. The servos cost US$2.75 each [0] and you need three of them plus a fairly beefy 5-volt power supply --- the USB ports on your laptop are not going to cut it. But the big issue is the Pi. The cheapest Raspberry Pi I can find locally (that isn't a Pico) is a Raspberry Pi 400, which is US$92 [1]. For some reason a bare Pi 4B is US$230 [2], and even a 3B is US$130 [3].
I had the impression that the Pi didn't have hardware PWM, but the pigpio library used [4] says it supports hardware PWM and thus servo pulses on pins 0-31. (Shows what I know.) So if your Linux process gets delayed because the CPU is busy, it might cause arm movements to pause, but it won't command the servo to move to a wildly different position.
Still, I feel like an Arduino or Pico sort of thing would be a better fit. Much cheaper and no worries about pauses. A BluePill costs about US$11 [5] and an ESP32 is about US$7.10 [6]. That's still not quite cheap enough to hit US$15 but it might fit into 15 euros. Can the BrachioGraph software be hacked to run in MicroPython?
(I calculated all these prices using AR$207/US$ but that was the price yesterday; apparently today the peso is worth 7% less and it's AR$222/US$, so adjust accordingly.)
The PantoGraph [7] looks more appealing to me because its parallel kinematics remove the need to move heavy servomotors around.
I had the impression that the Pi didn't have hardware PWM, but the pigpio library used [4] says it supports hardware PWM and thus servo pulses on pins 0-31. (Shows what I know.) So if your Linux process gets delayed because the CPU is busy, it might cause arm movements to pause, but it won't command the servo to move to a wildly different position.
Still, I feel like an Arduino or Pico sort of thing would be a better fit. Much cheaper and no worries about pauses. A BluePill costs about US$11 [5] and an ESP32 is about US$7.10 [6]. That's still not quite cheap enough to hit US$15 but it might fit into 15 euros. Can the BrachioGraph software be hacked to run in MicroPython?
(I calculated all these prices using AR$207/US$ but that was the price yesterday; apparently today the peso is worth 7% less and it's AR$222/US$, so adjust accordingly.)
The PantoGraph [7] looks more appealing to me because its parallel kinematics remove the need to move heavy servomotors around.
[0]: https://articulo.mercadolibre.com.ar/MLA-619943977-mini-serv...
[1]: https://articulo.mercadolibre.com.ar/MLA-905167031-computado...
[2]: https://articulo.mercadolibre.com.ar/MLA-876846669-raspberry...
[3]: https://articulo.mercadolibre.com.ar/MLA-1143260129-raspberr...
[4]: http://abyz.me.uk/rpi/pigpio/index.html
[5]: https://articulo.mercadolibre.com.ar/MLA-737177975-modulo-de...
[6]: https://articulo.mercadolibre.com.ar/MLA-916790826-nodemcu-e...
[7]: https://www.brachiograph.art/how-to/pantograph.html