{"id":1021,"date":"2022-09-07T10:10:20","date_gmt":"2022-09-07T09:10:20","guid":{"rendered":"https:\/\/bassett.me\/mike\/blog\/wordpress\/?p=1021"},"modified":"2022-09-07T10:16:16","modified_gmt":"2022-09-07T09:16:16","slug":"discharge-wand","status":"publish","type":"post","link":"https:\/\/bassett.me\/mike\/blog\/wordpress\/shed\/discharge-wand\/","title":{"rendered":"Discharge Wand"},"content":{"rendered":"\n

While working on high voltage power supplies – several hundred volts – I often found myself needing to discharge capacitors which had retained thier high voltage after power had been removed. Note that it is definately not a good idea to just short out the terminals, you may get a satisfying bang but it will damage your capacitor – it may not be immediatly obvious but it will reduce it’s capabilities. The method I used was to place a resistor across the connections. This had disadvantages: You had to hold the resistor on the high voltage terminals somehow and you didn’t know when the voltage had reduced to a safe level. So I designed a circuit which would make both these easier. <\/p>\n\n\n\n

Note that this circuit is not suitable for low voltages which can still cause damage to your circuitry; I recommend an LED in series with a suitable resistor for these; make sure you’ve got it the right way round! <\/p>\n\n\n\n

I put the wand in a small box with a fixed probe on the box and a probe on a flexible lead. There is an LED which illuminates as long as the voltage exceeds 24V; as 30V and below is considered safe voltage I think this is adequate. It is designed to go up to 500V but may go a little higher; especially if the capacitor is small in value. The voltage that mine will take is a bit limited as it is built on stripboard, if you build it on a better material it could go much higher, especially if you increase the value of R1 – R4. These resistors have to have a sufficiently high power rating for the voltage as it may take several minutes to discharge a large capacitor and the circuit takes up to 50mA. <\/p>\n\n\n\n

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500V discharge wand<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"

While working on high voltage power supplies – several hundred volts – I often found myself needing to discharge capacitors which had retained thier high voltage after power had been […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[3],"tags":[],"_links":{"self":[{"href":"https:\/\/bassett.me\/mike\/blog\/wordpress\/wp-json\/wp\/v2\/posts\/1021"}],"collection":[{"href":"https:\/\/bassett.me\/mike\/blog\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/bassett.me\/mike\/blog\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/bassett.me\/mike\/blog\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/bassett.me\/mike\/blog\/wordpress\/wp-json\/wp\/v2\/comments?post=1021"}],"version-history":[{"count":2,"href":"https:\/\/bassett.me\/mike\/blog\/wordpress\/wp-json\/wp\/v2\/posts\/1021\/revisions"}],"predecessor-version":[{"id":1029,"href":"https:\/\/bassett.me\/mike\/blog\/wordpress\/wp-json\/wp\/v2\/posts\/1021\/revisions\/1029"}],"wp:attachment":[{"href":"https:\/\/bassett.me\/mike\/blog\/wordpress\/wp-json\/wp\/v2\/media?parent=1021"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/bassett.me\/mike\/blog\/wordpress\/wp-json\/wp\/v2\/categories?post=1021"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/bassett.me\/mike\/blog\/wordpress\/wp-json\/wp\/v2\/tags?post=1021"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}