Picaxe driving mains switching
- Thread starter malti
- Start date
The simple rule for any mains switching is that if you don't know what you are doing then do not do it.
How best and most safely do mains switching depends on a number of factors; what's being switched, what mains voltage, what load, what type of load, load operating characteristics and a number of other factors.
As for ringing the church bells - what would the circuit be controlling ? I assume there's some electro-mechanical device which will go between any PICAXE circuit and the bells.
How best and most safely do mains switching depends on a number of factors; what's being switched, what mains voltage, what load, what type of load, load operating characteristics and a number of other factors.
As for ringing the church bells - what would the circuit be controlling ? I assume there's some electro-mechanical device which will go between any PICAXE circuit and the bells.
fernando_g
Senior Member
Agree with hippy about knowing the risks and pitfalls associated with working with powerline voltages.
A TRIAC driven by a suitable optocoupler is the way to go. However if your loads are highly inductive, and your switching is slow enough, then a relay could be better.
How large is your load (in amps)?
A TRIAC driven by a suitable optocoupler is the way to go. However if your loads are highly inductive, and your switching is slow enough, then a relay could be better.
How large is your load (in amps)?
Picaxe driving mains switching
Thanks guys for ur reply
I am technical ok, but not familiar with triacs, diacs etc. I guess relays with a good current/voltage rating would do it , but fear mechanical parts.
A friend of mine is having problems with keeping church bells ringing primarily becuse it uses an old system of relays ,solinoids, turrets, push pins rolling drums etc. I would like to design a Picaxe 18X based system.
Any suggestions or where to search on the web ? please
Thanks
Paul
Thanks guys for ur reply
I am technical ok, but not familiar with triacs, diacs etc. I guess relays with a good current/voltage rating would do it , but fear mechanical parts.
A friend of mine is having problems with keeping church bells ringing primarily becuse it uses an old system of relays ,solinoids, turrets, push pins rolling drums etc. I would like to design a Picaxe 18X based system.
Any suggestions or where to search on the web ? please
Thanks
Paul
BeanieBots
Moderator
The comments made so far remain valid.
The circuit design will depend on the load. You can't just take any old triac driving circuit and expect it to work on any old load. For example, a highly inductive load on a simple DC level controlled triac will never switch off. A very capacitive load with a pulse triggered triac will never switch on.
What was the cause of failure on the old system? Contact welding?
Most relays are mechanically OK for about 1E6 operations. Earlier failure suggests a design fault. Same is likely to happen to a triac except a melted triac will also take out whatever is driving it.
The circuit design will depend on the load. You can't just take any old triac driving circuit and expect it to work on any old load. For example, a highly inductive load on a simple DC level controlled triac will never switch off. A very capacitive load with a pulse triggered triac will never switch on.
What was the cause of failure on the old system? Contact welding?
Most relays are mechanically OK for about 1E6 operations. Earlier failure suggests a design fault. Same is likely to happen to a triac except a melted triac will also take out whatever is driving it.
When you say "old system", how old? Are parts obsolete? It may be that you can easily "renovate" the system, whole scale replacing the "mechanical" parts of the system, to make it reliable again.
It might be worth considering renovating the bell "interface" of relays and solinoids and only using the PICaxe to replace the push pin rolling drum - I presume this is a "music box" style controller to play a repetative peel.
The renovation could allow you to choose a relay coil voltage that can be interfaced easily, while keeping the solinoid voltages on the contact side of the circuit.
Given the number of cycles a relay can perform, it's not un reasonable to consider like for like changes.
best regards,
colin
Picaxe driving mains switching
Thanks all for reponse.
The system is old, I guess I still have to keep the mechanics, but did not want to add more mechanical relays.
Yes, the Picaxe 18 will control 6 ac relays to drive solinoids to make the bells ring a tune.
Paul
Thanks all for reponse.
The system is old, I guess I still have to keep the mechanics, but did not want to add more mechanical relays.
Yes, the Picaxe 18 will control 6 ac relays to drive solinoids to make the bells ring a tune.
Paul
premelec
Senior Member
I have used opto isolators driven by a PICAXE switching triacs - however this is basically what a solid state relay is so probably best to just use commercial solid state relays - they usually take a few milliamperes of current to switch on. Note that a triac - and most solid state relays for power - stay on until current through them is greatly reduced... this happens naturally with AC on the zero current crossings [which are out of phase with the voltge for inductive loads] to the load. If the actuators are DC controlled you have a different situation. Sometimes DC is used to avoid mechanical buzz AC could cause [e.g. in pipe organ valves...] - look into what you've got carefully. Mechanical relays are still used a lot and are mechanically noisier but also easier to trouble shoot by just looking at them! Study up on inductive kickback suppression and opto iscolators.... Klack on!
From a safety and cost point of view, the best approach might be to buy a remotely controlled mains outlet socket (for dimming lights etc) from the likes of B&H or Homebase. I have not looked at the operation of these units in detail but they probably use standard IR transmission techniques/codes to remotely control a triax. The high voltage circuitry is fully enclosed and terminated in a 3-pin mains socket and the optical link should provide an additional level of safety.
If you buy one of these units and can’t make a PICAXE mimic a standard hand held controller, you can always revert to using the controller for its original domestic purpose.
If you buy one of these units and can’t make a PICAXE mimic a standard hand held controller, you can always revert to using the controller for its original domestic purpose.
BeanieBots
Moderator
That's because there's so much more to a mains circuit than just the diagram.
Also, people are always reluctant to give advice on something which can kill.
How do you think the "reply poster" would feel if the parents of the originator came on line and said,
"our little Johny built the circuit you described, he's now dead after electrocuteing himself because you forget to mention that the triac tab would be at mains voltage so he touched the heatsink and died. We will be persuing a claim."?
Also, home wiring in the UK is now illegal unless done (or inspected & passed) by a qualified engineer.
Mycroft2152
Senior Member
Little Johnny would be awarded the DARWIN award--posthumously of course.
What's all this with Electronic Church Bells? I almost fell off my penny farthing. Here in the City of Churches (Adelaide) we use a team of people to do the job. And a very tricky job it is too, because the bells ring several seconds after you pull the rope.
Newfangled machines. Pah!
Newfangled machines. Pah!
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