pootle
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Control board for a central heating style pump with dutycycle control

Mon Jan 13, 2020 12:08 pm

I want to control a standard mains central heating type pump from a Raspberry pi, with some basic control of speed. Presumably something with opto isolator in it, or driven with an rf signal

Most of the stuff I've found uses relays (really? relays still?) like this one, which would clearly not work for speed control apart from loosing the benefits of a zero crossing triac.

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mahjongg
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Re: Control board for a central heating style pump with dutycycle control

Tue Jan 14, 2020 3:50 pm

Most motors don't work with electronic dimmers, as "speed control" devices, so no "duty-cycle control" other than a few seconds on/off is possible, and yes relays are still the main way to do it.

p.s. as real children sometimes attempt to do stuff like this (they have not learnt how deadly mains can be) some visitors here (who cannot guess how old you are) can react protective, don't get angry when they do :| ..... :mrgreen:

p.s.s. driven with an RF signal? :roll: How do you imagine that? RF mean Radio Frequency, or do you mean something else. Please explain.

p.s.s.s I decided to remove all the previous bickering, to start over with a clean slate.

pootle
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Re: Control board for a central heating style pump with dutycycle control

Wed Jan 15, 2020 8:31 am

mahjongg wrote: Most motors don't work with electronic dimmers, as "speed control" devices, so no "duty-cycle control" other than a few seconds on/off is possible.
I'm specifically interested in central heating pump type motors (Grundfos etc), Don't care about most motors. I have a control unit on 1 that does control its' speed (and not on / off for seconds at a time, so I know it can be done.
mahjongg wrote: and yes relays are still the main way to do it.
And still an unreliable way to do it compared to using triacs. My experience of mains switches (X10 and some more modern units) using relays, is that they are far less reliable than old light dimmer switches. Yes the X10 probably used cheap relays, but then the dimmer switches were also probably built to a price. I only stopped using light dimmer controls 25 years ago when we switched all our light bulbs to fluorescents in a new house.
mahjongg wrote: p.s.s. driven with an RF signal? :roll: How do you imagine that? RF mean Radio Frequency, or do you mean something else. Please explain.
All I'm saying is that I don't much care much how the signal from the pi gets to the motor control widget. Many similar things use opto isolators, driven by logic level signals, I've seen similar devices that connect over USB. I'd be quite happy with a "separate" box controlled by bluetooth or driven over spi, It doesn't have to be physically wired to the pi, although I wouldn't want to have to use yet another wall wart power supply.

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rpdom
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Re: Control board for a central heating style pump with dutycycle control

Wed Jan 15, 2020 8:47 am

pootle wrote:
Wed Jan 15, 2020 8:31 am
mahjongg wrote: Most motors don't work with electronic dimmers, as "speed control" devices, so no "duty-cycle control" other than a few seconds on/off is possible.
I'm specifically interested in central heating pump type motors (Grundfos etc), Don't care about most motors. I have a control unit on 1 that does control its' speed (and not on / off for seconds at a time, so I know it can be done.
Is that full variable speed, or a number of set speeds? IIRC the Grundfos pump on my heating system just has three speed settings, probably using different combinations of coils on the motor so not something that can be controlled externally.
pootle wrote:
mahjongg wrote: and yes relays are still the main way to do it.
And still a crap unreliable way to do it compared to using triacs. My experience of mains switches (X10 and some more modern units) using relays, is that they are far less reliable than old light dimmer switches. Yes the X10 probably used cheap relays, but then the dimmer switches were also probably built to a price. I only stopped using light dimmer controls 25 years ago when we switched all our light bulbs to fluorescents in a new house.
Fluorescents? Are you still using that ancient technology? All LED lights here, some with dimmers :)

Oh, by the way, I control my central heating from a Pi with a relay, but I don't worry about speeds, just the temperature.
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mahjongg
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Re: Control board for a central heating style pump with dutycycle control

Wed Jan 15, 2020 10:52 am

pootle wrote:
Wed Jan 15, 2020 8:31 am

And still a crap unreliable way to do it compared to using triacs. My experience of mains switches (X10 and some more modern units) using relays, is that they are far less reliable than old light dimmer switches. Yes the X10 probably used cheap relays, but then the dimmer switches were also probably built to a price. I only stopped using light dimmer controls 25 years ago when we switched all our light bulbs to fluorescents in a new house.
Triac dimmers are fine for heating elements (purely resistive loads) but are unsuitable for any kind of inductive loads, including all motors.
The very sharp edges generated by a triac dimmer don't play well with inductors, and would generate massive EMF voltages when current through the inductance is suddenly started 50/60 times a second.

Some things are simply not "dimmable", and yes fluorescent lightening is one of them, motors are another, and many LED modules too (they start to flicker at low settings).

P.S. By the way, when anyone wonders what happened to previous posts that disappeared, I deleted them because of their conflicting nature, I wanted to wipe the slate clean, so we could start anew, without the sideshow.
Lets be positive, and not immediately assume other people are idiots that don't know that mains voltages are dangerous.

That the world still relies on relays has a reason. :ugeek:

I would call the service-desk of grundfos to ask how the pump speed can be regulated.

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Re: Control board for a central heating style pump with dutycycle control

Wed Jan 15, 2020 11:02 am

rpdom wrote:
Wed Jan 15, 2020 8:47 am
Is that full variable speed, or a number of set speeds? IIRC the Grundfos pump on my heating system just has three speed settings, probably using different combinations of coils on the motor so not something that can be controlled externally.
The pump does have 3 preset speeds, but the controller also (claims) to additionally control the speed to quite low rates
rpdom wrote:
Wed Jan 15, 2020 8:47 am
Fluorescents? Are you still using that ancient technology? All LED lights here, some with dimmers :)
Well strange as it may seem, I'm not still buying the same type of lights as I did 25 years ago, for the last 15 years (ish) it's been LEDs, although I only ditched the last compact flourescent a few months ago - the one in the loft still worked, but was really dim on switch on (and getting dimmer) and took longer and longer to warm up, but I only go up there a couple of times a year. All led now with some philips Hue and some ikea tradfri (but hooked up to the hue controller).
rpdom wrote:
Wed Jan 15, 2020 8:47 am
Oh, by the way, I control my central heating from a Pi with a relay, but I don't worry about speeds, just the temperature.
The smart controller is on a solar hot water system and uses a resol controller, (a much earlier version of this..) but I want to put in a more sophisticated control of the CH pump to help keep the boiler at maximum efficiency, and without giving away all my data to google.

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Re: Control board for a central heating style pump with dutycycle control

Wed Jan 15, 2020 11:53 am

OK, so I'm getting multiple reports on this thread, for various reasons, so not happy.

Apparently safety related posts were deleted, offensive posts not so. I cannot undelete, but have edited out bad language I have spotted.

So I'm closing it to draw a line. Please start a new thread, please keep it civil, and please keep safe when using main voltage.
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Re: Control board for a central heating style pump with dutycycle control

Wed Jan 15, 2020 1:32 pm

@Jamesh The "safety related" posts, were only in the style of "kids should not do this kind of stuff", and the backlash to it. These posts were all deleted, and in actuality we already restarted the whole thread, so I'm unlocking. Sorry.

@davicoton, sorry that I am upsetting you, I'm not trying to block "safety information", its just that your reaction caused a big backlash, and it seemed better to reset the thread.

If you have valid safety info please add it to this thread, but remember that you are not talking to a kid, it seems the OP is knowledgeable enough to know what he is doing.

is difficult to keep everybody happy... :|

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Re: Control board for a central heating style pump with dutycycle control

Wed Jan 15, 2020 6:02 pm

pootle wrote:
Wed Jan 15, 2020 11:02 am
I only ditched the last compact fluorescent a few months ago - the one in the loft still worked, but was really dim on switch on
Yeah, they do that which is a really annoying feature of CFLs. In my loft I have a twin 2ft tube old fashioned 18W fluorescent fitting. The only reason I haven't replaced it is because a) I almost never go up there (once in the last 5 years) and b) it still works fine. :)
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Re: Control board for a central heating style pump with dutycycle control

Wed Jan 15, 2020 6:39 pm

rpdom wrote:
Wed Jan 15, 2020 6:02 pm
pootle wrote:
Wed Jan 15, 2020 11:02 am
I only ditched the last compact fluorescent a few months ago - the one in the loft still worked, but was really dim on switch on
Yeah, they do that which is a really annoying feature of CFLs. In my loft I have a twin 2ft tube old fashioned 18W fluorescent fitting. The only reason I haven't replaced it is because a) I almost never go up there (once in the last 5 years) and b) it still works fine. :)
I replaced the 5FT T8 strips in my garage with 5FT LED lights (and a starter that simply shorts the contacts)
https://www.lightbulbs-direct.com/cromp ... light-2ft/
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Re: Control board for a central heating style pump with dutycycle control

Wed Jan 15, 2020 8:48 pm

DougieLawson wrote:
Wed Jan 15, 2020 6:39 pm
rpdom wrote:
Wed Jan 15, 2020 6:02 pm
pootle wrote:
Wed Jan 15, 2020 11:02 am
I only ditched the last compact fluorescent a few months ago - the one in the loft still worked, but was really dim on switch on
Yeah, they do that which is a really annoying feature of CFLs. In my loft I have a twin 2ft tube old fashioned 18W fluorescent fitting. The only reason I haven't replaced it is because a) I almost never go up there (once in the last 5 years) and b) it still works fine. :)
I replaced the 5FT T8 strips in my garage with 5FT LED lights (and a starter that simply shorts the contacts)
https://www.lightbulbs-direct.com/cromp ... light-2ft/
The replacement for the starter should be fused at the appropriate rating, as the commercially available replacements are. Not a simple link.

EDIT: Typo
Last edited by davidcoton on Wed Jan 15, 2020 10:07 pm, edited 1 time in total.
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Re: Control board for a central heating style pump with dutycycle control

Wed Jan 15, 2020 9:00 pm

DougieLawson wrote:
Wed Jan 15, 2020 6:39 pm
rpdom wrote:
Wed Jan 15, 2020 6:02 pm
pootle wrote:
Wed Jan 15, 2020 11:02 am
I only ditched the last compact fluorescent a few months ago - the one in the loft still worked, but was really dim on switch on
Yeah, they do that which is a really annoying feature of CFLs. In my loft I have a twin 2ft tube old fashioned 18W fluorescent fitting. The only reason I haven't replaced it is because a) I almost never go up there (once in the last 5 years) and b) it still works fine. :)
I replaced the 5FT T8 strips in my garage with 5FT LED lights (and a starter that simply shorts the contacts)
https://www.lightbulbs-direct.com/cromp ... light-2ft/
I'm still not going to bother to replace a light that uses about 100mWh/year. No point.
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