Interesting Circuit From EDN to Measure 0 – 1000 Volts With a '555

[For The Popcorn]

EDN posted an interesting circuit to measure from 0 volts – 1000 volts with good resolution using the ever popular 555 chip and a single micro GPIO pin. Not that I have had much need to measure high DC voltages, but the idea is fantastic.

I'll leave the explanation of how it works to the article (linked above, PDF below). The circuit is dead simple (speaking of dead, be careful around high voltages), depending on the charging time of a capacitor. Complexity and component costs are low.

 

[ZipZapOuch]

My favorite part of this circuit is the quote from the designer " and it never really over-ranges". It's so nice when you think you're dealing with a 1kv source but it's really 30kV - that way you don't have to worry about fuses or other anomalies.

 

[schmitt trigger]

The 555 is such a versatile device!

 

[For The Popcorn]

The 555 is such a versatile device!

A 50 year old chip still produced by billions a year, with not-easy duplicated functions. Not bad!

 

[Nigel Goodwin]

A 50 year old chip still produced by billions a year, with not-easy duplicated functions. Not bad!

Hardly, more accurately it's probably the most misused chip there is, as in this example. As for 'not easily duplicated', it's easily replaced by a simple 8 pin PIC with FAR superior performance, and requiring many less external components.

You rarely see the 555 used commercially, and you rarely ever did - so I'm dubious about your claimed 'billions' made per year?.

 

[Inquisitive]

According to Wikipedia they make over a billion 555 per year.

 

[For The Popcorn]

....so I'm dubious about your claimed 'billion....

I expect nothing less from you. "Billions" come from a variety of industry sources. I am certain those several sources have more knowledge on the subject than me.

 

[ronsimpson]

Notice it is not a LM555 but a LMC555.

 

[ZipZapOuch]

I'm waiting for that time where I just can't get myself to use my CATIII 1000V (8000V transients) meter and cables to measure a 1000V supply and need to fabricate a mashup like this instead.

 

[Nigel Goodwin]

I'm waiting for that time where I just can't get myself to use my CATIII 1000V (8000V transients) meter and cables to measure a 1000V supply and need to fabricate a mashup like this instead.

Does that mean you can't measure the HT voltage in microwave ovens?.

We used to have one old Avo 8 which went to 3000V, and was enough to check microwave ovens - none of the other Avo 8's went quite high enough.

 

[ZipZapOuch]

Does that mean you can't measure the HT voltage in microwave ovens?.

We used to have one old Avo 8 which went to 3000V, and was enough to check microwave ovens - none of the other Avo 8's went quite high enough.

No, I'm saying, why would I rig up a 555 timer to measure a 1000v source when I have a meter designed and safety-certified to measure 1000V.

 

[AnalogKid]

Woodward is an exceptional circuit designer and the only real successor to Jim Williams - but - I don't think this is his best work.

ak

 

[AnalogKid]

You rarely see the 555 used commercially, and you rarely ever did -

I did.

I've seen in in telecom, medical, and MIL devices/applications/systems/whatever. And, I've designed it into all three of those spaces. While I'm in no way a "555 anywhere/everywhere" guy, sometimes it's the right tool for the job.

About 30 years ago I had an opportunity to review the schematic of a well known, high-density DC/DC converter. Boing - there it was.

ak

 

[ZipZapOuch]

About 5-years ago, my wife asked me to fix her coffee grinder. I opened it up and was surprised to find a NE555 DIP on a small PCB with a slider switch. The circuitry was fine for a 55-year-old design. The coffee bean oil was swelling the plastic and making the safety switch stick.

Since it was a nice Braun, I tosses it in the bin and told her it was irreparable. She enjoyed a day at the mall.