Re: [EE]: Flame rectification

On Fri, 19 Dec 2025, Brooke wrote:

> Hi Bob:
>
> I think this is the same system used on my gas stove cook top.
> PS sometimes there's a problem of not enough spark to light a burner.  Any 
> ideas of why?

immediate thought is air / gas ratio is wrong. check jets are clean.

>
> -- 
> Have Fun,
>
> Brooke Clarke
> https://www.PRC68.com
> axioms:
> 1. The extent to which you can fix or improve something will be limited by 
> how well you understand how it works.
> 2. Everybody, with no exceptions, holds false beliefs.
>
> -------- Original Message --------
>> Date: Fri, 19 Dec 2025 06:37:01 +0000
>> From: Bob Blick<[email protected]>
>> To: "Microcontroller discussion list - Public."<[email protected]>
>> Subject: [EE]: Flame rectification
>> Message-ID:
>> 
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>> 
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>>
>> I was doing a cleaning of my gas-fired forced air furnace, and it got me 
> thinking about how wonderfully designed it must be. It has a Honeywell S8610U 
> "Intermittent Pilot" module that combines both high(15KV-ish) voltage 
> ignition and low(80VAC-ish) voltage, low(5uA-ish) current flame detection on 
> the same wire and electrode. Fantastic. Especially since this very module has 
> been running since 1997, with very little maintenance, and has not missed a 
> beat.
>>
>> Has anyone reverse engineered the in and outs of this device and can 
> describe the circuitry, and how flame detection doesn't die the first time 
> the high voltage comes on? And how it can toggle between the two modes so 
> quickly and reliably?
>>
>> For those who haven't encountered it, the module runs on 24VAC, generates a 
> recurring high voltage spark at twelve Hz, energizes a pilot gas valve, 
> senses the pilot ignition on the same wire using flame rectification (in 
> between the high voltage sparks) and energizes the main gas valve if there is 
> a pilot flame present, then stops the HV and continues to monitor the flame. 
> It sounds like bzz-click-bzz-thunk-whoosh when starting. Quite obsolete by 
> today's standards, of course. It was built to last almost forever :)
>>
>> Thanks! Bob
>
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