Here's a tricky car question for the thinkers here

[Michael C]

I have 2 thermo fans and want to run them in three different ways

1) Off
2) In series so each sees 6V and runs around half speed
3) In parallel so each sees 12V and runs at full speed.

I'm planning to use relays to switch between these three modes. What's the
minimum number of relays I can use?

Michael

[atec]

Michael C wrote:
> I have 2 thermo fans and want to run them in three different ways
>
> 1) Off
> 2) In series so each sees 6V and runs around half speed
> 3) In parallel so each sees 12V and runs at full speed.
>
> I'm planning to use relays to switch between these three modes. What's the
> minimum number of relays I can use?
>
> Michael
>
>
On the E series ford does it with two relays .. off and two speeds.

[Vincent]

"Michael C" <me@nospam.com> wrote in message
news:429d117d$0$18643$14726298@news.sunsite.dk...
> I have 2 thermo fans and want to run them in three different ways
>
> 1) Off
> 2) In series so each sees 6V and runs around half speed
> 3) In parallel so each sees 12V and runs at full speed.
>
> I'm planning to use relays to switch between these three modes. What's the
> minimum number of relays I can use?
>
> Michael

Two relays. one extra switch

[Michael C]

"atec" <atec77@XXXhotmail.com> wrote in message
news:429d18e0$1@dnews.tpgi.com.au...
> On the E series ford does it with two relays .. off and two speeds.

Do they use a resistor to drop it to 6volts though?

Michael

[dale-google@monsya.net]

Use three relays. This way there is a separate relay for each fan, so
if a single relay failed, there would still be a fan able to be powered
up.

Feed each fan off a separate 2 pole, 2 position relay. The NO inputs
should connect to +12 and Gnd. The NC inputs should be connected in
series to the other relay with one tied to 12v and the other to Gnd.
When these relays cut in, you get full speed.

Another relay can be used in series with the power feed to these NC
connections. This gives you the half-speed setting when the two 'fan'
relay aren't on.

At least at half speed, these things don't sound like 747's taking off,
unlike a DC16 fan.

Dale.


Michael C wrote:
> "atec" <atec77@XXXhotmail.com> wrote in message
> news:429d18e0$1@dnews.tpgi.com.au...
> > On the E series ford does it with two relays .. off and two speeds.
>
> Do they use a resistor to drop it to 6volts though?
>
> Michael

[athol]

atec <atec77@xxxhotmail.com> wrote:
> Michael C wrote:
>> I have 2 thermo fans and want to run them in three different ways

>> 1) Off
>> 2) In series so each sees 6V and runs around half speed
>> 3) In parallel so each sees 12V and runs at full speed.

>> I'm planning to use relays to switch between these three modes. What's the
>> minimum number of relays I can use?

> On the E series ford does it with two relays .. off and two speeds.

If you are using ordinary generic relays, you'd need 2 changeover and one
normal relay to do it.

If an existing vehicle runs them in series on low using 2 relays, one of
them is likely to be a double relay with an internal link between 2
contacts such that there are 4 pins on the outside for the contacts
including an earth - could be a 5-pin relay if they use a common earth
or a common +12V pin between the contacts and solenoid.

Of course, some vehicles simply run only one fan for low and both for
high...

--
Athol
<http://cust.idl.com.au/athol> Linux Registered User # 254000
The state of infrastructure in New South Wales is a disgrace.
I'm a Libran Engineer. I don't argue, I discuss.

[Vinnie]

"Michael C" <me@nospam.com> wrote in message
news:429d117d$0$18643$14726298@news.sunsite.dk...
> I have 2 thermo fans and want to run them in three different ways
>
> 1) Off
> 2) In series so each sees 6V and runs around half speed
> 3) In parallel so each sees 12V and runs at full speed.
>
> I'm planning to use relays to switch between these three modes. What's the
> minimum number of relays I can use?
>
> Michael
>
> E-mail me at destef1@bigpond.com and I will e-mail you a simple wiring
diagram (schematic) using 2 relays.

Thanks
Regards
Vince

[Patrick Young]

Michael C wrote:
> I have 2 thermo fans and want to run them in three different ways
>
> 1) Off
> 2) In series so each sees 6V and runs around half speed
> 3) In parallel so each sees 12V and runs at full speed.
>
> I'm planning to use relays to switch between these three modes. What's the
> minimum number of relays I can use?
>
> Michael

For not exactly kosher, *minimum* relays would be one, however two
should be used (the extra for the main +12v feed).

The switching between series and parallel would use a relay with
a pair of contacts and a large diode between the -ve of one fan
and the +ve of the other fan.

|-relay1contact1----|
| |
+12v---relay2---fan1--->BigDiode|---fan2---Gnd
| |
|--relay1contact2---|

Don't be scared to use semiconductors around fans. Once had to
design up a regulator for an old 6V Studebaker HVAC fan once
the car had been converted to 12V. Before I did this the owner
actually drilled and centre tapped the battery!

[Scotty]

"Michael C" <me@nospam.com> wrote in message
news:429d117d$0$18643$14726298@news.sunsite.dk...
>I have 2 thermo fans and want to run them in three different ways
>
> 1) Off
> 2) In series so each sees 6V and runs around half speed
> 3) In parallel so each sees 12V and runs at full speed.
>
> I'm planning to use relays to switch between these three modes. What's the
> minimum number of relays I can use?
>
> Michael
>

Id say one changeover relay and a couple of Diodes.

[Scotty]

"Scotty" <noricer@comeagain.com> wrote in message
news:42a0cbfe$0$28224$afc38c87@news.optusnet.com.a u...
>
> "Michael C" <me@nospam.com> wrote in message
> news:429d117d$0$18643$14726298@news.sunsite.dk...
>>I have 2 thermo fans and want to run them in three different ways
>>
>> 1) Off
>> 2) In series so each sees 6V and runs around half speed
>> 3) In parallel so each sees 12V and runs at full speed.
>>
>> I'm planning to use relays to switch between these three modes. What's
>> the minimum number of relays I can use?
>>
>> Michael
>>
>
> Id say one changeover relay and a couple of Diodes.
>
DOH, nah,tried drawing that and need two changeover relays I think.

Hmm will try again

[Patrick Young]

Scotty wrote:
> "Scotty" <noricer@comeagain.com> wrote in message
> news:42a0cbfe$0$28224$afc38c87@news.optusnet.com.a u...
>
>>"Michael C" <me@nospam.com> wrote in message
>>news:429d117d$0$18643$14726298@news.sunsite.dk...
>>
>>>I have 2 thermo fans and want to run them in three different ways
>>>
>>>1) Off
>>>2) In series so each sees 6V and runs around half speed
>>>3) In parallel so each sees 12V and runs at full speed.
>>>
>>>I'm planning to use relays to switch between these three modes. What's
>>>the minimum number of relays I can use?
>>>
>>>Michael
>>>
>>
>>Id say one changeover relay and a couple of Diodes.
>>
>
> DOH, nah,tried drawing that and need two changeover relays I think.
>
> Hmm will try again

One diode and one DPST relay - already posted the diagram. Typical
applications of using a diode to break a series circuit is a charge
pump where you charge capacitors in parallel and discharge in series
for things like 6vdc to 9vdc adaptors etc, or more interestingly -5vdc
from 9vdc.

[Scotty]

"Patrick Young" <patrick@hilux.ace.unsw.EDU.AU> wrote in message
news:rM9oe.2059$F7.104@news-server.bigpond.net.au...
> Scotty wrote:
>> "Scotty" <noricer@comeagain.com> wrote in message
>> news:42a0cbfe$0$28224$afc38c87@news.optusnet.com.a u...
>>
>>>"Michael C" <me@nospam.com> wrote in message
>>>news:429d117d$0$18643$14726298@news.sunsite.dk...
>>>
>>>>I have 2 thermo fans and want to run them in three different ways
>>>>
>>>>1) Off
>>>>2) In series so each sees 6V and runs around half speed
>>>>3) In parallel so each sees 12V and runs at full speed.
>>>>
>>>>I'm planning to use relays to switch between these three modes. What's
>>>>the minimum number of relays I can use?
>>>>
>>>>Michael
>>>>
>>>
>>>Id say one changeover relay and a couple of Diodes.
>>>
>>
>> DOH, nah,tried drawing that and need two changeover relays I think.
>>
>> Hmm will try again
>
> One diode and one DPST relay - already posted the diagram. Typical
> applications of using a diode to break a series circuit is a charge
> pump where you charge capacitors in parallel and discharge in series
> for things like 6vdc to 9vdc adaptors etc, or more interestingly -5vdc
> from 9vdc.

Well, bugger me, yourve blown my theory to peices with something thats
obviously wayyy more advanced, Ill just go crawl back into my hovel and
watch.............

[atec]

Patrick Young wrote:
> Michael C wrote:
>
>> I have 2 thermo fans and want to run them in three different ways
>>
>> 1) Off
>> 2) In series so each sees 6V and runs around half speed
>> 3) In parallel so each sees 12V and runs at full speed.
>>
>> I'm planning to use relays to switch between these three modes. What's
>> the minimum number of relays I can use?
>>
>> Michael
>
>
> For not exactly kosher, *minimum* relays would be one, however two
> should be used (the extra for the main +12v feed).
>
> The switching between series and parallel would use a relay with
> a pair of contacts and a large diode between the -ve of one fan
> and the +ve of the other fan.
>
> |-relay1contact1----|
> | |
> +12v---relay2---fan1--->BigDiode|---fan2---Gnd
> | |
> |--relay1contact2---|
>
> Don't be scared to use semiconductors around fans. Once had to
> design up a regulator for an old 6V Studebaker HVAC fan once
> the car had been converted to 12V. Before I did this the owner
> actually drilled and centre tapped the battery!
what rating do you suggest on the diode ?. ( farkin big one)

[Patrick Young]

atec wrote:

> what rating do you suggest on the diode ?. ( farkin big one)

SF61 (Jaycar). Product code ZR-1092 should do it.

As each fan is getting around 6 volts, the current in the
circuit is halved. These are 6 Amp diodes.

I have no idea what fans are required in this case, however
you could put more diodes if required in parallel for higher
current.

I'm not sure if you would need to use a low value resistor

----\/\/\/---->|----
---| |---
----\/\/\/---->|----

to make up for spec differences in the mfg run of the diodes.

[atec]

Patrick Young wrote:
> atec wrote:
>
>> what rating do you suggest on the diode ?. ( farkin big one)
>
>
> SF61 (Jaycar). Product code ZR-1092 should do it.
>
> As each fan is getting around 6 volts, the current in the
> circuit is halved. These are 6 Amp diodes.
>
> I have no idea what fans are required in this case, however
> you could put more diodes if required in parallel for higher
> current.
>
> I'm not sure if you would need to use a low value resistor
>
> ----\/\/\/---->|----
> ---| |---
> ----\/\/\/---->|----
>
> to make up for spec differences in the mfg run of the diodes.
Wekk the fans on the Ford draw about 20 amps surge to operate then
settle down to a couple of amps , Ill stick with 2 realays thanks .

[athol]

Patrick Young <patrick@hilux.ace.unsw.edu.au> wrote:
> atec wrote:

>> what rating do you suggest on the diode ?. ( farkin big one)

> SF61 (Jaycar). Product code ZR-1092 should do it.

> As each fan is getting around 6 volts, the current in the
> circuit is halved. These are 6 Amp diodes.

> I have no idea what fans are required in this case, however
> you could put more diodes if required in parallel for higher
> current.

Much better to simply use the NC and NO contacts in the relays and not
need a diode at all...

I'll approach it as standard off-the-shelf automotive relays, although I
suspect that more specific types may exist...

Earth Low/High +12V Off/On
| | | |
+-------+-------|--------+------------|----+ |
| | +--------|-------+ | | |
| | | | | | | |
| [ +--///--+ ] [ +--///--+ ] | [ +--///--+ ]
| [(-) sol (+)] [(-) sol (+)] | [(-) sol (+)]
| [ relay 3 ] [ relay 2 ] | [ relay 1 ]
| [ NC com NO ] [ NC com NO ] | [ com NO ]
| [ +--\ --+ ] [ +--\ --+ ] | [ \ --+ ]
| | | | | | | | | |
| +---|---|--------+ | | +--------+ |
| | +------------|---|-----------------+
+-----------|----------------|---+ |
| | | |
+--[fan 2]--+ +------[fan 1]--------+

--
Athol
<http://cust.idl.com.au/athol> Linux Registered User # 254000
The state of infrastructure in New South Wales is a disgrace.
I'm a Libran Engineer. I don't argue, I discuss.

[Patrick Young]

atec wrote:

> Wekk the fans on the Ford draw about 20 amps surge to operate then
> settle down to a couple of amps , Ill stick with 2 realays thanks .

SF61 peak forward surge current 150 Amps.

While I'm a fan of ancient computers, I'm not one of
relay powered equipment :-p

OTOH there's also a small 8 pin DIP switch mode PS
controller/MOSFET IC I'm not that happy with either ATM as
Athol knows about, and I had to buy a whole new PS as
can't get the IC in less than 3000 quantities :-(

[Lily Lubis, attorney at law]

On 04 Jun 2005 08:12:04 GMT, athol <me@privacy.net> wrote:

>
>Much better to simply use the NC and NO contacts in the relays and not
>need a diode at all...
>
>I'll approach it as standard off-the-shelf automotive relays, although I
>suspect that more specific types may exist...
>

i looked at this for 10 mins and i get it now. this puts 6V across
both fans in Lo and 12V off the Relay 1 output on Hi.

perhaps i can study this in more depth after you put me in prison with
your legal action :)

--

Lily Lubis (Ms)
Attorney at Law
5/37 Paknabiel Way
Denpasar, Indonesia.

Defamation cases our speciality!

[atec]

Patrick Young wrote:
> atec wrote:
>
>> Wekk the fans on the Ford draw about 20 amps surge to operate then
>> settle down to a couple of amps , Ill stick with 2 realays thanks .
>
>
> SF61 peak forward surge current 150 Amps.
that would do the job with a suitable heat sink . but the transient
time of application would need watching with out one .
>
> While I'm a fan of ancient computers, I'm not one of
> relay powered equipment :-p
I am , it breaks you replace it and its a simple plug job , mind I
like gas carbys as well.
>
> OTOH there's also a small 8 pin DIP switch mode PS
> controller/MOSFET IC I'm not that happy with either ATM as
> Athol knows about, and I had to buy a whole new PS as
> can't get the IC in less than 3000 quantities :-(
number ?
I have access to several tons of good shite.

[Patrick Young]

athol wrote:

> Much better to simply use the NC and NO contacts in the relays and not
> need a diode at all...

Nothing wrong with that (however no power to coils on
switching relays mean no fans in the event of relay contact
failure, and low speed requires two ferpect electrical
contacts so getting back into the diode stuff), however
the original Q was minimum # of relays. I'd expect if a mfg
was serious about it ...

> suspect that more specific types may exist...

A specific in house design part, and part number would
emerge as a single {expensive} FRU.

> Earth Low/High +12V Off/On
> | | | |
> +-------+-------|--------+------------|----+ |
> | | +--------|-------+ | | |
> | | | | | | | |
> | [ +--///--+ ] [ +--///--+ ] | [ +--///--+ ]
> | [(-) sol (+)] [(-) sol (+)] | [(-) sol (+)]
> | [ relay 3 ] [ relay 2 ] | [ relay 1 ]
> | [ NC com NO ] [ NC com NO ] | [ com NO ]
> | [ +--\ --+ ] [ +--\ --+ ] | [ \ --+ ]
> | | | | | | | | | |
> | +---|---|--------+ | | +--------+ |
> | | +------------|---|-----------------+
> +-----------|----------------|---+ |
> | | | |
> +--[fan 2]--+ +------[fan 1]--------+