{"id":27915459,"url":"https://github.com/aabbtree77/k155-clock","last_synced_at":"2026-01-24T21:08:23.747Z","repository":{"id":246211738,"uuid":"820296418","full_name":"aabbtree77/K155-clock","owner":"aabbtree77","description":"K155 series clock with gas discharge displays.","archived":false,"fork":false,"pushed_at":"2025-04-14T12:34:40.000Z","size":900,"stargazers_count":0,"open_issues_count":0,"forks_count":0,"subscribers_count":1,"default_branch":"main","last_synced_at":"2025-04-14T13:48:05.954Z","etag":null,"topics":["chemistry","cupric-sulfate","digital-clock","electrolysis","electronics","etching","ferric-chloride","gas-discharge-displays","hardware","hydrochloric-acid","k155","manufacturing","microchip","pcb","plasma","printing","retrocomputing","ussr"],"latest_commit_sha":null,"homepage":"","language":null,"has_issues":true,"has_wiki":null,"has_pages":null,"mirror_url":null,"source_name":null,"license":"mit","status":null,"scm":"git","pull_requests_enabled":true,"icon_url":"https://github.com/aabbtree77.png","metadata":{"files":{"readme":"README.md","changelog":null,"contributing":null,"funding":null,"license":"LICENSE","code_of_conduct":null,"threat_model":null,"audit":null,"citation":null,"codeowners":null,"security":null,"support":null,"governance":null,"roadmap":null,"authors":null,"dei":null,"publiccode":null,"codemeta":null,"zenodo":null}},"created_at":"2024-06-26T07:35:30.000Z","updated_at":"2025-04-14T12:34:43.000Z","dependencies_parsed_at":null,"dependency_job_id":"bb795cad-c45d-422b-941f-0b2e66c59f03","html_url":"https://github.com/aabbtree77/K155-clock","commit_stats":null,"previous_names":["aabbtree77/mona-lisa","aabbtree77/k155-clock"],"tags_count":0,"template":false,"template_full_name":null,"repository_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/aabbtree77%2FK155-clock","tags_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/aabbtree77%2FK155-clock/tags","releases_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/aabbtree77%2FK155-clock/releases","manifests_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories/aabbtree77%2FK155-clock/manifests","owner_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners/aabbtree77","download_url":"https://codeload.github.com/aabbtree77/K155-clock/tar.gz/refs/heads/main","host":{"name":"GitHub","url":"https://github.com","kind":"github","repositories_count":252717810,"owners_count":21793376,"icon_url":"https://github.com/github.png","version":null,"created_at":"2022-05-30T11:31:42.601Z","updated_at":"2022-07-04T15:15:14.044Z","host_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub","repositories_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repositories","repository_names_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/repository_names","owners_url":"https://repos.ecosyste.ms/api/v1/hosts/GitHub/owners"}},"keywords":["chemistry","cupric-sulfate","digital-clock","electrolysis","electronics","etching","ferric-chloride","gas-discharge-displays","hardware","hydrochloric-acid","k155","manufacturing","microchip","pcb","plasma","printing","retrocomputing","ussr"],"created_at":"2025-05-06T15:54:35.603Z","updated_at":"2026-01-24T21:08:23.668Z","avatar_url":"https://github.com/aabbtree77.png","language":null,"funding_links":[],"categories":[],"sub_categories":[],"readme":"\u003e Dedicated to my father.\n\n\u003ctable\u003e\n\u003ctr\u003e\n\u003cth style=\"text-align:center\"\u003e A Home-Made Digital K155 Clock, circa 1992\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cimg src=\"./images/mona-main.jpg\"  alt=\"My Mona Lisa: A Digital Clock based on the Soviet K155 series microchips\" width=\"100%\" \u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/table\u003e\n\nSoviet TTL K155-series microchips, gas discharge displays. The electric circuit diagram seems to be lost.\n\n# Photos\n\n\u003ctable\u003e\n\u003ctr\u003e\n\u003cth style=\"text-align:center\"\u003e Inside the Box\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cimg src=\"./images/mona-open.jpg\"  alt=\"My Mona Lisa: My Mona Lisa: Inside the Box\" width=\"100%\" \u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/table\u003e\n\n\u003ctable\u003e\n\u003ctr\u003e\n\u003cth style=\"text-align:center\"\u003e Circuit Board: Top\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cimg src=\"./images/mona-board-top.jpg\"  alt=\"My Mona Lisa: Top of Circuit Board\" width=\"100%\" \u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/table\u003e\n\n\u003ctable\u003e\n\u003ctr\u003e\n\u003cth style=\"text-align:center\"\u003e Circuit Board: Bottom\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cimg src=\"./images/mona-board-bottom.jpg\"  alt=\"My Mona Lisa: Bottom of Circuit Board\" width=\"100%\" \u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/table\u003e\n\n\u003ctable\u003e\n\u003ctr\u003e\n\u003cth style=\"text-align:center\"\u003e Voltage Transformer\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cimg src=\"./images/mona-transformer.jpg\"  alt=\"My Mona Lisa: Voltage Transformer\" width=\"100%\" \u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/table\u003e\n\n\u003ctable\u003e\n\u003ctr\u003e\n\u003cth style=\"text-align:center\"\u003e Gas Discharge Displays\u003c/th\u003e\n\u003c/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\n\u003cimg src=\"./images/mona-indicators.jpg\"  alt=\"My Mona Lisa: Gas Discharge Displays\" width=\"100%\" \u003e\n\u003c/td\u003e\n\u003c/tr\u003e\n\u003c/table\u003e\n\n# Details\n\n## Circuit Board Printing\n\nWe used a single copper (Cu) plated board, the routes were drawn with a nail polish followed by the immersion into **ferric chloride (Fe2Cl3)** to etch the circuit routes, later replaced with **Cupric sulfate CuSO4**. The etching got faster, but not by much.\n\nThe fastest way is electrolysis, but the nail polish would not protect the routes well. \n\nThe printed routes were never of high quality.\n\nThis design is flawed in that there is too much copper to remove.\n\n## 220/9/5\n\nAt the time it was common to build voltage transformers manually. We had a lot of varnished copper wire of old circuit relays floating around. The formula was surprisingly simple: \n\n** # windings/volt  = 50/S,** \n\nwhere S was an effective area of a ferrite core entering the transformer's casing, in squared centimeters.\n\nThis would work for a vast range of transformer and wire sizes, but extra-compact transformers would demand extremely thin copper wire which would not support enough power to drive a neighbour's portable cassette Sony Walkman used as a desktop cassette recorder ;).\n\nConsider an exercise to derive this formula from Maxwell's equations...\n\n","project_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Faabbtree77%2Fk155-clock","html_url":"https://awesome.ecosyste.ms/projects/github.com%2Faabbtree77%2Fk155-clock","lists_url":"https://awesome.ecosyste.ms/api/v1/projects/github.com%2Faabbtree77%2Fk155-clock/lists"}