| jarthel |
I intend to buy a 10V relay. Can I use a varying DC supply of 9.5V to around 10.4V supply?
Thank you. |
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| poobah |
Yes... there is generally a little "give" in the coil specs. The absolute limits should be listed in the relay's data sheet though. You ARE talking about thew coil rating right?
:) |
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| jarthel |
| quote: | Originally posted by poobah
Yes... there is generally a little "give" in the coil specs. The absolute limits should be listed in the relay's data sheet though. You ARE talking about thew coil rating right?
:) |
yes I'm talking about the coil.
unfortunately, I can't see the voltage operating range in the datasheet. all I see is the 10V (nominal).
thank you. |
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| poobah |
A 10 Volt relay would probably "pick up" at 6 Volts and "drop out" at around 4 Volts. So your safe at 9 Volts, easy, on the low side. Your limiter on the high side is power dissipation in the coil. You're safe to assume a +/- 10% on coil voltage.
:) |
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| mrshow4u |
| it's a 10V 32.5mA 550mW 182 Ohm coil 3A contacts It doesn't give pull in or hold current specs. I think 9V would be easy. |
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| rpapps |
Hi Jarthel
From my reading of the datasheet, it looks like its good for from 6.3 to 13.4 volts.
Cheers
Rob |
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| AndrewT |
Hi,
it looks like the low operate voltage using 182r and 32.5mA is about 6V. Well below your 9.5V.
The release voltage is only quoted as the minimum, in other word,s the voltage below which you must reduce to guarantee release.
The maximum release is what some relays will start to drop out at. You will need to measure this for your relay. |
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| jarthel |
| quote: | Originally posted by AndrewT
Hi,
it looks like the low operate voltage using 182r and 32.5mA is about 6V. Well below your 9.5V. |
where did you see this? |
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| jarthel |
also can I use this relay for 240VAC?
I saw in the datasheet something like
"maximum switching voltage: 250VAC"
"UL contact rating: 30V/1A or 100V/.3A"
Thanks again |
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| poobah |
Yes you can...
Be very mindful of one thing that relates to switches... of any type... toggles, relays, etc... The AC voltage and current ratings have NOTHING to do with the DC ratings. AC circuits have a big advantage... every 8.3 or 10 milliseconds the current goes to zero. This helps extinguish the arc. So... DC ratings for voltage and current are always much lower for the same relay (with a few exceptions).
Where are you wanting to use these relays? There are some things you should know about low level circuits maybe.
:) |
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| jarthel |
| quote: | Originally posted by poobah
Where are you wanting to use these relays? There are some things you should know about low level circuits maybe.
:) |
I am planning to use this relay to turn-on the primaries for the B+ transformer. I will connect the primaries to the "normally-open" pins.
this is the circuit: http://myweb.tiscali.co.uk/nuukspot...c/555delay2.gif
I have a separate 9V transformer for the amp tubes' heaters. I'll use the voltage (which varies from 9.5 to 10.3 according to simetrix) on the 1st cap as +V input to the NE555. |
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| poobah |
That sounds fine...
Consider carefully your inrush currents at turn on.
The amount of current the relay must open is actually more important than the closure current. Do you have PSUDII?
This can give you inrush roughly... |
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| jarthel |
| quote: | Originally posted by poobah
That sounds fine...
Consider carefully your inrush currents at turn on.
The amount of current the relay must open is actually more important than the closure current. Do you have PSUDII?
This can give you inrush roughly... |
I will be using an ntc thermistor at the primary. should that affect the operation? |
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| poobah |
Yes,
That will help greatly. You can push the amperage ratings a wee bit where inrush is concerned... maybe a factor of 2 would be prudent. It is the interrupting (opening) ratings that you can't ignore.
Now, the relays aren't characterized that way... they give you one rating... illegitimate offsprings! You can generally assume the ratings refer to opening and not closing.
:) |
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| jarthel |
| thank you very much for all the help :) |
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| poobah |
you are most welcome...
Sorry if I explain things a little reluctant... gotta watch your rear around here.
You ask a lot of well thought out questions.
:) |
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| jarthel |
just found this datasheet(http://relays.tycoelectronics.com/datasheets/d2n.pdf)
ul contact rating:
30 Vdc / 1.0 A
100 Vdc / 0.3 A
125 Vac / 0.5 A for 150 mW and 200 mW coil
125 Vac / 1.0 A for 400 mW and 500 mW coil
does that mean I can't use 240VAC on it? current draw would be less than 500mA for the B+ supply and the amp current load (not including heaters as the amp tube's heaters are powered using a 2nd transformer). |
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| poobah |
That's correct... you need a relay with a higher AC rating I'm afraid...
Tyco's website is just loads of fun... ain't it?
:headbash: |
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| rpapps |
Hi Jarthel
At the risk of throwing in another confusion factor, how about something like this.
It's an SY-4080 from Jaycar Electronics. |
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| rpapps |
Here's the datasheet.
Cost $12.
Cheers
Rob |
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| jarthel |
| quote: | Originally posted by rpapps
Hi Jarthel
At the risk of throwing in another confusion factor, how about something like this.
It's an SY-4080 from Jaycar Electronics. |
do you think it would work with the ne555 circuit above? |
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| rpapps |
Hi
You would need a small modification to the circuit.
The 555 output goes low (to ground) to operate the mechanical relay whereas the SS relay requires a positive voltage of 3 or more so you need a transistor to invert that signal.
Cheers
Rob |
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| jarthel |
using a mechanical relay, one side of the coil is connected to the reset of the ne555 (pin8) and the other side is connected to trigger (pin7)
with your changes, what happens to these connections? |
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| rpapps |
Hi
The relay is actually connected to pin 3 (output) and pin 4 which is connected to the + supply. Neither of the two diodes shown would be needed. My mod would take its input from pin 3 and its + and ground connections from the equivalent pins on the 555.
Cheers
Rob |
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| jarthel |
| quote: | Originally posted by rpapps
ground connections from the equivalent pins on the 555.
Cheers
Rob |
do you mean power supply ground? cause the only ground connection of the 555 is connected to power supply ground. |
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| rpapps |
Hi
Yes that's right.
I simplified the circuit a bit.
Cheers
Rob |
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| jarthel |
| quote: | Originally posted by rpapps
Hi
Yes that's right.
I simplified the circuit a bit.
Cheers
Rob |
I assume the "reset" pin of the n3555 is not needed anymore? |
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| rpapps |
| Yes it is. Just leave it connected to the + supply as shown in your original circuit. |
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| jarthel |
| quote: | Originally posted by rpapps
Yes it is. Just leave it connected to the + supply as shown in your original circuit. |
thank you very much. looking for a relay that will work in either 9 or 10V is so hard in this country! :| even when looking at RS |
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| jarthel |
| any suggestion for a bc108 substiute? that's available in jaycar? |
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| rpapps |
Hi
You're welcome.
Perhaps this will make it clearer for you.
PN100 will do as a substitute (Catalog # ZT-2283) and cheap @ $0.25.
Cheers
Rob |
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| jarthel |
| thank you for the help |
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| rpapps |
Hi Jarthel
I thought about it some more and it can be done more simply.
Cheers
Rob |
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| jarthel |
| quote: | Originally posted by rpapps
Hi Jarthel
I thought about it some more and it can be done more simply.
Cheers
Rob |
any reason for the change? also, why is the "-" pin of the relay on the trigger? (i think it's the trigger)
thanks again |
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| mrshow4u |
...instead of inverting the state of the output of the 555, couldn't you just "tug" on the low side of the SS relay's LED?? and have the Hi side pulled up to supply
....oops, I saw above post . Sorry for being late:bawling: :smash: |
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| rpapps |
Hi Jarthel
Reason for change is just to make it simpler - fewer parts, easier to make. I should have thought of it earlier but I'm >57 and not as quick as I used to be.
The + of the relay goes to + supply via the current limiting resistor and the - of the relay is pulled to ground by the 555 output. It's just another way of defurring a feline.
Cheers
Rob |
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| jarthel |
| the original circuits uses diodes (possibly for protection). do I need to put them back? |
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| poobah |
Jarthel,
Every relay (almost) should have a diode across its coil. Sometimes, it can be confusing which way to place the diode... simple, place the diode so the diode does NOT conduct while the relay is "ON".
:) |
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| rpapps |
Hi Jarthel
Poobah is correct for mechanical relays as they can produce a high reverse voltage across the coil when the current is turned off. The diode absorbs this and prevents damage to other components.
However, this is a solid state relay and does not produce the inductive kickback so no diodes are necessary. You are only switching current through a LED.
Cheers
Rob |
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