I've searched here and the internet, but I can't find a simple picture/explanation about how to wire up a relay using 240V.
I need to implement a basic soft start circuit (Figure 1 at this link ), but I don't know how to connect all the pins. Can someone please give an idiots guide to this?
I've been quite proud of myself up until now as I've managed to work out wiring schematics, chip and transistor connections, etc, but this one really has me stumped.
I think I need a Sinle pole normally on relay which has 4 connectors, but again advice on this would also be appreciated.
It's only to try and stop my 300VA torroid from blowing fuses at switch on time - I know it shouldn't need a soft start circuit, but mine does.
I need to implement a basic soft start circuit (Figure 1 at this link ), but I don't know how to connect all the pins. Can someone please give an idiots guide to this?
I've been quite proud of myself up until now as I've managed to work out wiring schematics, chip and transistor connections, etc, but this one really has me stumped.
I think I need a Sinle pole normally on relay which has 4 connectors, but again advice on this would also be appreciated.
It's only to try and stop my 300VA torroid from blowing fuses at switch on time - I know it shouldn't need a soft start circuit, but mine does.
yes,
you need the normally open contacts for the bypass function.
They close when power is sent to the relay coil.
A change over relay has this function, just leave the third pin empty.
Have a look at fig 4 for the power saving circuit.
It allows the relay to drop out more quickly.
Combine fig3 with fig4 to operate the relay coil from any higher supply voltage. eg the relay coil could be 12Vdc but run from 20 to 28Vdc and the timer circuit can be on the 15V or 12V supply.
you need the normally open contacts for the bypass function.
They close when power is sent to the relay coil.
A change over relay has this function, just leave the third pin empty.
Have a look at fig 4 for the power saving circuit.
It allows the relay to drop out more quickly.
Combine fig3 with fig4 to operate the relay coil from any higher supply voltage. eg the relay coil could be 12Vdc but run from 20 to 28Vdc and the timer circuit can be on the 15V or 12V supply.
There are much simpler/cheaper ways of doing what you want than the ESP site you referenced.
For example by using the charging of bulk caps on the XFMR secondary to power the relays coil. This has a built in delay that is usually good enough for the job at hand.
On a chip amp you could use a 48V/24V relay coil with a series resistor across 1/2 of the DC supply. The series resistor drops the excess PS voltage to the relay coils. I've done this successfully a number of times before.
For example by using the charging of bulk caps on the XFMR secondary to power the relays coil. This has a built in delay that is usually good enough for the job at hand.
On a chip amp you could use a 48V/24V relay coil with a series resistor across 1/2 of the DC supply. The series resistor drops the excess PS voltage to the relay coils. I've done this successfully a number of times before.
I did this for a GFA-555 amp in a past thread here.
Tell me what you want ie what transformer and good UK source for relay parts.
Basically you need 3 parts
1) 2 ohm, 5 or 10 Watt sand cast resistor (Rsurge) in series with the transformers primary winding. Rsurge is wired between the fuse and the XFRMR primary leg.
2) relay - 24 V or 48 V coil SPDT w/ contacts rated for 240V and current greater than VA. Way of mounting the relay for point to point wiring or PCB/perfboard with all three parts near the AC input fuse.
3) Resistor in series with relay coil , where
Rd = (Vout -Vrelay)/Icoil,
This will drop excess voltage from Vout to reach the coil turn on V.
Rd in series with relay coil both across one or both of your output caps whichever is close to your relay coils voltage.
Operation on start
Rsurge limits the current inrush in the transformer primary until the the relay energizes thus bypassing Rsurge.
The relay switch contacts (pole) and (normally open) will be wired in parallel with Rsurge.
The relay won't energize untill the outputs come up.
Tell me what you want ie what transformer and good UK source for relay parts.
Basically you need 3 parts
1) 2 ohm, 5 or 10 Watt sand cast resistor (Rsurge) in series with the transformers primary winding. Rsurge is wired between the fuse and the XFRMR primary leg.
2) relay - 24 V or 48 V coil SPDT w/ contacts rated for 240V and current greater than VA. Way of mounting the relay for point to point wiring or PCB/perfboard with all three parts near the AC input fuse.
3) Resistor in series with relay coil , where
Rd = (Vout -Vrelay)/Icoil,
This will drop excess voltage from Vout to reach the coil turn on V.
Rd in series with relay coil both across one or both of your output caps whichever is close to your relay coils voltage.
Operation on start
Rsurge limits the current inrush in the transformer primary until the the relay energizes thus bypassing Rsurge.
The relay switch contacts (pole) and (normally open) will be wired in parallel with Rsurge.
The relay won't energize untill the outputs come up.
Infinia
Thanks for the reply.
I've got a 240V AC, 300VA, 25V dual secondary torroid.
Parts supplier for me would be Farnell in the UK http://uk.farnell.com/
Of the relays they stock then here are the items that match your description Relays.
However, I can see only one that matches your specs and that's this one
As for Rd, can you give me a worked example to understand that calculation - basically I'm confused as to what Volts you're referring to (i.e, mains volts, or DC volts).
And the final question for now, Output cap? Where are those?
Thanks for the reply.
I've got a 240V AC, 300VA, 25V dual secondary torroid.
Parts supplier for me would be Farnell in the UK http://uk.farnell.com/
Of the relays they stock then here are the items that match your description Relays.
However, I can see only one that matches your specs and that's this one
As for Rd, can you give me a worked example to understand that calculation - basically I'm confused as to what Volts you're referring to (i.e, mains volts, or DC volts).
And the final question for now, Output cap? Where are those?
Andrew
Thanks for the spreadsheet and inevitably I have questions !!
Relay pull in and Relay drop out voltages - How do I determine those? i.e, how do I know what value to enter here?
I'm guessing that R1 is wired in series between the live terminal of the fused IEC socket and the live terminal on the relay?
I assume the value given for R1 at the end of the calculation will be enough to drop the mains 230V voltage down to the 24V rating of the relay - Correct or incorrect?
Thanks
Thanks for the spreadsheet and inevitably I have questions !!
Relay pull in and Relay drop out voltages - How do I determine those? i.e, how do I know what value to enter here?
I'm guessing that R1 is wired in series between the live terminal of the fused IEC socket and the live terminal on the relay?
I assume the value given for R1 at the end of the calculation will be enough to drop the mains 230V voltage down to the 24V rating of the relay - Correct or incorrect?
Thanks
NO NO NO.
It works off a DC supply!!!!!!!
Note the use of semiconductors and diodes. Mains AC would kill this circuit.
The relay should be measured to obtain the pull in and drop out voltages.
The coil resistance can be checked but the manufacturer's specification is likely to be quite close.
Most relays operate on DC supplies.
Some are made and specified to operate on AC supplies.
Your linked one is for 24Vdc.
If you don't learn to read the data and spec sheets, you are putting yourself and others at risk of serious harm.
It works off a DC supply!!!!!!!
Note the use of semiconductors and diodes. Mains AC would kill this circuit.
The relay should be measured to obtain the pull in and drop out voltages.
The coil resistance can be checked but the manufacturer's specification is likely to be quite close.
Most relays operate on DC supplies.
Some are made and specified to operate on AC supplies.
Your linked one is for 24Vdc.
If you don't learn to read the data and spec sheets, you are putting yourself and others at risk of serious harm.
Ok, this is where my confusion lies.
My understanding is the relay will slow the inrush of current to the transformer, so how does it do that if it has DC connected to it? Surely DC is only obtainable after the torroid is switched on and current flowing from the bridge unit? That means the transformer is drawing power and to me that means it'll blow the fuse.
I know I'm missing something pretty fundamental here as the whole point of the circuit is to stop the inrush, but I'm struggling.
My understanding is the relay will slow the inrush of current to the transformer, so how does it do that if it has DC connected to it? Surely DC is only obtainable after the torroid is switched on and current flowing from the bridge unit? That means the transformer is drawing power and to me that means it'll blow the fuse.
I know I'm missing something pretty fundamental here as the whole point of the circuit is to stop the inrush, but I'm struggling.
Whilst you have been helpful, Andrew, I do take exception to that comment.
The whole point of this thread was to learn, from very simple basics, how relays are wired. So far nobody has answered that question - you all assume that I know how they must be wired up, but I don't.
I know they are DC items, but no explanation I've seen actually discusses how you get DC into the relay.
So, can someone please explain in very basic terms how they work.
Thank you.
infinia said:
Hi yes that relay works
Find Icoil from data sheet http://uk.farnell.com/tyco-electronics-schrack/ry210024/pcb-relay-contacts-spdt/dp/1652615
Icoil = Vrelay/Rcoil =24/2350 = 0.01 A
Now find the dropping resistor in series with the relay coil (both wired across one DC output bulk cap.
Rd = (Vo-Vrelay)/Icoil =((24*1.414 - 1.4) -24)/0.01 = 853 use 860 ohms 1/4 watt
where Vo is the rectified PS secondary across one of the output bulk caps.
PS I tried Andrew SS but it didn't work somehow
westers151 said:
The heart of this simple inrush current limiter circuit is the 5 watt power resistor in series with the transformer.
The relay contacts just short out the resistor after the output voltage reaches close to its normal level. This is to take it out of the circuit after it's done. If you didn't have the relay contacts to " short out" the resistor the transformer wouldn't get all its power. In case of a "fault" the resistor mostly would burn up protecting the transformer if per chance there was a short somewhere in the secondary or even the PS output.
Thanks Infinia - I'm starting to understand it a little better now.
However, I'm still struggling to understand how to wire all of this up. Can you shed some light on this?
I understand the Rsurge fuse - that's connected between the live terminal on my fused switch and the live wire on the primary winding of my transformer.
However, how do I connect up the relay - that's DC, but your comments that the relay switch contacts Pole and normally open are wired in parallel with RSurge, which suggests it's exposed to AC.
Sorry if I'm being dumb, but electronics is new to me and this is stumping me. Contrary to other comments, I'm loathe to do anything without first understanding/confirming that it works.
Thanks
However, I'm still struggling to understand how to wire all of this up. Can you shed some light on this?
I understand the Rsurge fuse - that's connected between the live terminal on my fused switch and the live wire on the primary winding of my transformer.
However, how do I connect up the relay - that's DC, but your comments that the relay switch contacts Pole and normally open are wired in parallel with RSurge, which suggests it's exposed to AC.
Sorry if I'm being dumb, but electronics is new to me and this is stumping me. Contrary to other comments, I'm loathe to do anything without first understanding/confirming that it works.
Thanks
Hi westers
Relays are a way to switch high power stuff using a small safe current. read the link below and then reread the posts above again.
http://electronics.howstuffworks.com/relay1.htm
Relays are a way to switch high power stuff using a small safe current. read the link below and then reread the posts above again.
http://electronics.howstuffworks.com/relay1.htm
Hi,
go and read ESP's various papers on power supplies and transformers and delay circuits and soft starts etc.
http://sound.westhost.com/project39.htm
go and read ESP's various papers on power supplies and transformers and delay circuits and soft starts etc.
http://sound.westhost.com/project39.htm
Hi Westers
This site has loads of introductory type info on it. They have forums also, so someone may have asked the question before and had an answer you can follow.
Don't get disheartened, everyone has to start somewhere unless you were born with a soldering iron in your hand. I'm sure your mother would have mentioned it if you were!
I have a couple of 300VA toroid powered chipamps without softstart that switch on fine with a 3.15A fuse, and have done so for a couple of years now on the same fuse.
A 2 amp fuse will turn the amp on as long as the source isn't playing, but it will blow if the amp has to jump straight into amplifying.
John
This site has loads of introductory type info on it. They have forums also, so someone may have asked the question before and had an answer you can follow.
Don't get disheartened, everyone has to start somewhere unless you were born with a soldering iron in your hand. I'm sure your mother would have mentioned it if you were!
I have a couple of 300VA toroid powered chipamps without softstart that switch on fine with a 3.15A fuse, and have done so for a couple of years now on the same fuse.
A 2 amp fuse will turn the amp on as long as the source isn't playing, but it will blow if the amp has to jump straight into amplifying.
John
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