[{"data":1,"prerenderedAt":229},["ShallowReactive",2],{"project-45954228":3},{"id":4,"name":5,"line":6,"line_source":7,"title":8,"url":9,"domain":10,"maker":11,"posted_at":12,"year":13,"points":14,"comments":15,"rank_in_year":16,"shown_in_year":17,"top":18,"tier":19,"category":20,"subcategory":21,"format":20,"keywords":22,"reception":27,"sentiment":28,"stance_mix":29,"scored_comments":33,"aspects":34,"strip":41,"post_text":42,"what":43,"said":53,"maker_in_thread":116,"shape":126,"grid":131,"attempts":192,"same_week":193,"maker_shows":31,"maker_hidden":222,"reader_version":223,"card":224},"45954228","2025","32V TENS device from built from scratch under $100","title","Show HN: 32V TENS device from built from scratch under $100","https:\u002F\u002Flittlemountainman.github.io\u002F2025\u002F11\u002F17\u002Ftens\u002F","littlemountainman.github.io","autonomydriver",1763391992,2025,70,25,1008,3837,27,"notable","hardware","medical device",[23,24,25,26],"tens device","diy electronics","electrotherapy","nerve stimulation","roasted",-0.5,{"positive":30,"neutral":31,"mixed":30,"critical":32},0,2,5,7,{"execution":35,"docs":37,"idea":39,"pricing":40},{"positive":30,"critical":36},3,{"positive":30,"critical":38},1,{"positive":30,"critical":30},{"positive":30,"critical":38},[38,30,38,30,30,30,36,30,30,30,30,30,38,30,30,30,30,30,30,30,30,30,38,36,38],null,{"problem":42,"audience":42,"pricing":44,"motivation":42,"time_to_build":42,"stack":50,"openness":51,"stage":52,"team_size":51},{"value":45,"source":46,"evidence":47},"Built for under $100 total cost","maker",[48],{"id":49},"post",[],"unknown","prototype",{"praise":54,"objections":55,"requests":102,"questions":103,"alternatives":111},[],[56,67,74,84,95],{"value":57,"source":58,"evidence":59},"Monophasic output considered less safe than biphasic; maker plans it for a V2","commenter",[60,64],{"id":61,"by":62,"text":63},"46004576","lambdaone","Monophasic waveforms are generally considered less safe than biphasic waveforms. That's why many TENS units have an output stage based around a pulse transformer, so they can…",{"id":65,"by":11,"text":66},"46013830","Coming in a V2, semester just started again, so I have a little less time for it. Given that I also have some other projects on the way :)",{"value":68,"source":58,"evidence":69},"Safety concerns and high danger of building a stimulator at home",[70],{"id":71,"by":72,"text":73},"46005849","zhouyisu","I tried to build some TENS device, but lost in \"safety maze\". I reverse engineered some existing device, there are TONS of safety measures. At least: current limiting resistor,…",{"value":75,"source":58,"evidence":76},"Finger pad outputs wired together, contrary to the stated design",[77,81],{"id":78,"by":79,"text":80},"46004809","clnhlzmn","I see > Each electrode channel is tied to a finger pad but the layout shows the finger pads are all tied together. What am I missing?",{"id":82,"by":11,"text":83},"46013836","Poor wording, should mean that each finger has a dedicated output, but you are right, they are all tied together",{"value":85,"source":58,"evidence":86},"Battery discharge cutoff voltage of 3.0V questioned",[87,91],{"id":88,"by":89,"text":90},"46002308","dmitrygr","> down to ~3.0V (discharged). That is NOT how one uses lithium batteries one foe snot want to go boom. Consider 3.6V as empty. Discharging them down to 3.0 can cause them to go…",{"id":92,"by":93,"text":94},"46006192","shadowpho",">3.6V is considered the nominal voltage, certainly not the low end cut off. This is not right (3.6v certainly is and can be cut off depending on device and battery). One thing…",{"value":96,"source":58,"evidence":97},"Commercial TENS units cost much less on Amazon",[98],{"id":99,"by":100,"text":101},"46006254","NoSalt","This is cool, and all, but you can buy a TENS unit for $20.00 to $40.00 on Amazon.",[],[104],{"value":105,"source":58,"evidence":106},"What do people use TENS devices for?",[107],{"id":108,"by":109,"text":110},"46006956","arresin","What do people use this for?",[112],{"value":113,"source":58,"evidence":114},"Commercial TENS units sold on Amazon for $20 to $40",[115],{"id":99,"by":100,"text":101},{"comments":117,"answered":31,"key":118},4,[119,120,123],{"id":65,"text":66},{"id":121,"text":122},"46013800","The two BJTs do limit current to 20mA on all finger outputs. Voltage feedback is also set up to ensure maximum 32V. MCU protection, well just a ferrite bead.",{"id":124,"text":125},"46013831","In my searches, yes, I found something like that from an italian university. 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