Time delay relay- RC curcuit

[wagoon 2,429]

So I have been learning about time delay RC circuits trying to sort a setup out for wiring up my EL thermo fans.  Basically want I want to do is run the first fan off the first relay then have a time delay device in between the 1st and 2nd relay's so the 2nd relay is triggered say 10-20 seconds after the first relay is energised. I can work out how long the delay is if I know the resistor rating and the capacitor rating but I don't know if this sort of relay is even a time delay setup/RC circuit  https://www.autoelec.com.au/ssl/public_autoelec/store_v4/product_detail.asp?id=1859&cat=28  and whether it will work as the 2nd relay let alone know how to calculate the delay time if it does that function.

 

If the above relay isnt what I am after is there a relay out there that has the time delay built in or am I going to have to go to Jaycar and buy a board, resistors and capacitor and make it myself. The thing I am concerned about is from what I have read each fan pulls around 40 amp on startup and run at around 15amp once running. So the time delay system will need to withstand the 40amp pull on start up for the second fan.

 

Please don't tell me to just upgrade my alternator.

[hendrixhc 10,921]

RC circuits are old hat, go digital!

[hendrixhc 10,921]

http://www.godeal.com.ar/p/diy-ne555-monostable-switch-time-delay-circuit-module-red-12v-152890

 

Something like this.

 

Trigger the circuit of the contacts of the first fan relay.

[hendrixhc 10,921]

I used to make these sort of circuits 25 of years ago to run decade counters with digital displays.

[Jiminy Kriket 133]

Or you could go the way i have gone and run 2 separate temp switches in the water, 1 turns on at 85 degrees, off at 80. The other turns on at 90 and off at 85. All i have done is run them to 2 separate relays and then powered each fan from there. Cost about $40 a switch.

[Xelisty 366]

One of these will do it http://m.supercheapauto.com.au/Product/Davies-Craig-Digital-Thermatic-Fan-Switch/374278

 

 

 

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[gerg 10,871]

Yeah I've given this some thought too, albeit with a series/parallel setup on 2 fans for hi/lo speed.

 

Also considered the second sender set at a higher temp, would be a simpler setup for sure.

 

There are industrial type relays that have time-on and time-off functions that are adjustable in various ranges of time. I have one that goes from 1-30 seconds. I'll see if I can dig it up and find the brand, etc.

[wagoon 2,429]

Thanks for all the reply's, I know pretty much nothing about the technical side of wiring. So all these ideas help me to learn more, keep them coming.

http://www.godeal.com.ar/p/diy-ne555-monostable-switch-time-delay-circuit-module-red-12v-152890

 

Something like this.

 

Trigger the circuit of the contacts of the first fan relay.

I realise that the RC circuit isn't the newest idea but it's simple as from what I can tell cheap. I do like the digital idea but one thing it says in the above link is says "Can control 220V /1A and below devices". If the fan is going to draw 40 amp on initial startup and 15ish amp continuous will this digital controller be able to cope with that sort of amp draw?

 

Or you could go the way i have gone and run 2 separate temp switches in the water, 1 turns on at 85 degrees, off at 80. The other turns on at 90 and off at 85. All i have done is run them to 2 separate relays and then powered each fan from there. Cost about $40 a switch.

I would rather have both fans come on a one temperature above the opening temp of my thermostat so that the thermostat isn't always opening and closing. I am using this Tridon switch to trigger the thermo fans

 

 

One of these will do it http://m.supercheapauto.com.au/Product/Davies-Craig-Digital-Thermatic-Fan-Switch/374278



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I would rather trigger the fans from direct water temp as I will be circuit racing not sure how both heat soak and constant high speed air flow would effect the probe in the radiator fins.

[gerg 10,871]

If your controller can't handle the amps, just relay it!

[wagoon 2,429]

If your controller can't handle the amps, just relay it!

Isn't the blue thing on the board in the pic a relay? Plus is there a point to having the first relay to turn on the first fan, then another relay before the board in the pic, then the last relay to turn on the second fan? My original idea of using the RC circuit was to keep the setup simple as I would buy a resistor and capacitor at specific values to give a specific time delay, once the capacitor is "full" it sends current to the second relay, I don't need displays or adjustability just to know how long it will take for the capacitor to "fill"

[Jiminy Kriket 133]

If you read the values on top of the relay on that board, it's only rated to 10 amps. You would need to feed a larger relay to run the thermo off that board.

[wagoon 2,429]

If I have to spend money on boards and extra relays I might as well buy a bigger alternator and not have to worry about any of this. I was hoping it would just be an easy fix but the more I look into it the, the better and easier the new alternator is sounds. Ah well there goes another couple hundred bucks

[hendrixhc 10,921]

I think it would be a good idea to beef up the alternator anyways.

 

The one in my XC was an easy replacement and provides 100A instead of the stock 40A.

 

Even though you are attempting to switch the to fans independently you still ending up drawing 30A-40A.

 

The board up above is only a switching device and as previously stated would be needed to drive a second relay for power purposes.

 

I hope this all makes sense as i just woke up!

[wagoon 2,429]

Yeah after reading my notes on relay's again I get what your saying about the trigger only. I was thing would need to feed power through the board not just the trigger. Probably make for a nicer install to with rhe board triggering the second relay.

I wasnt to concerned about my original 60amp alternator as its been checked and has a new bearing in it. I have zero power option so only factory stuff to draw current will be lights(wont be driving much at night anyway) speedo, tacho, radio and heater fan. The stuff I am adding like gauges and fuel pump only draw less than 10amp total between all of them.

But will go and have a chat to the local sparky as he's pretty good with older stuff so will see what he's got.

[wagoon 2,429]

Update:

For those that don't read my build thread I thought I would update this thread so hopefully someone gets use out of the outcome.

Thanks to Hendrixhc for the idea on using a time delay board as that's the way I went.

 

So this pic shows the delay board I bought off Ebay for $7, it's not exactly the one I wanted but it was what was available for fast delivery at the time. This board has 2 timed cycles and depending on how you wire it up is how it works, I have wired it so I get a delay time(I have set it for a 15 second delay to start) then after the delay cycle the board has a powered cycle and continues on like this as long as power is supplied . Once the thermatic switch is turned off when it reaches it's listed lower temp the relay board is reset and will start with the delay cycle once power is returned. So I have set it up to work for 15 second delay then 999 second powered cycle(maximum time allowed on the board, just over 16 minutes 35 seconds)

 

To house the delay board I went to Jaycar and bought a universal housing. There are a few options including metal and plastic housing, the one I bought was a water proof plastic housing. The delay board needed a slight adjusting on one of the holes to make it mount but I only mounted the board on 2 mounts, the board doesn't move at all with just the 2 mounts attached. The housing comes in a grey colour that can be seen in the first pic around the delay board, I just painted the housing with a satin black spray can with no sanding or anything. The housing cost me less than $20 and is completely waterproof has lots of mounting options and the cover of the houing can be removed with the base left in place as seen in the above picture.

 

[hendrixhc 10,921]

Nice work!