Relay that switches with only 5V?

[70XIN]

***DISREGARD EVERYTHING IN THE POST, I AM AN IDIOT - LOOK AT MY NEXT POST***


Hi guys,

I'm trying to put an F20C into a corolla.

The f20c ecu outputs 5V from one wire to trigger the s2000 fuel pump relay (i do not have this, nor the plugs/wiring associated).

As far as i can see, almost all lovely toyotas trigger the fuel pump/circuit open relay by grounding the FP wire. I was just going to try and stick with the stock COR.

I mindlessly bought a relay (tridon, 5 pin mini relay, 30amp, non resistor), thinking that i could simply switch this f20c 5V signal into an earth. 5V doesn't SEEM to be enough to trigger this particular relay.

What can/should i do? A few people have suggested buying a better/different relay - other people have suggested taking up knitting. I am pretty cool with either at this point.

***DISREGARD EVERYTHING IN THE POST, I AM AN IDIOT - LOOK AT MY NEXT POST***

[RA35GT]

Mate, couple options.

use a solid state relay or a transistor.

Jaycar had solid state relay which should be suitable. Probably the easiest way.

[VA61DETT]

Ok,

I really need to sleep but something like this should do the trick:



R1 can be around 330 ohms
D1 should be a high speed diode,a 1n4007 should do the trick (don't omit this otherwise the transistor will DIE)
Q1 BC639 NPN Transistor. (see Jaycar website)

Hope this helps.

-A

[70XIN]

Wow! Thanks guys

Turns out, after spending all night trying to work this POS out, i don't think the ECU is "supposed" to be giving off any voltage .. it's supposed to pull to ground (or as far as i can tell from the s2000 fuel pump relay, pictured below). A15 is the fuel pump output from the ECU, and the B1/B9 are ignition power.



The only information i can get from the S2000 manual, is that 'A15' should have "0V for 2 seconds after turning ignition switch on, then battery voltage". On my setup:

With the A15 wire connected to nothing, multimeter says 5V for 2 seconds, then no voltage.

With the A15 wire connected to the FP wire going into the AE86 COR, power drops slightly to 10-11V, and then straight back to 12V.

Unfortunately, i don't have headers/exhaust on the car yet, so i can't kick it over and see if the fuel pump wants to prime (actually i guess i could if i took out ignition coils).

I'm tired, i hate cars.

[river]

Hi,

If the relay needs to stay on after the 5V input (for 2 seconds) then just buy a 5V latching relay and connect up. They're only a couple of dollars, if that. Not sure if Jaycar has any latching relays.

If you are after such stuff - and other electronic devices, ICs, LEDs, etc etc - then go and check out Rockby (rockby.com.au) as they have a stack of stuff and very good prices - especially their weekly specials. I get most of my electronic components from them. I have some 5V latching relays at home, which I got from Rockby.

seeyuzz
river

[VA61DETT]

Sounds like the ECU has more or less the same drive arrangement as my previous circuit.
Most transistor switches work like this, i.e pulling to ground. This is due to the nature of the NPN device.

Most ECUs will usually only run the pump for a few seconds to 'prime' and then cut off if the engine is not running (for safety).
As soon as the crank angle / dizzy pulses are received it should kick up again.

-A

[70XIN]

Would there be any reason that it isn't grounding properly (only dips to 10-11V during the 2 seconds when you turn the key to ignition)?

[70XIN]

Oh, and i know (?) the AE86 fuel pump relay is still functioning properly - if i mindlessly just ground the FC wire coming out of it, the fuel pump runs.

[river]

Hi,

Ahhh... now I see. I can't get images in my explorer at work, but now that I'm home I can see your relay diagram.

I assume ST SWITCH is your starter. So, when you turn the key to start you will have 12v of power going into pin 2. Pin 1 should be earthed and this will complete the circuit and activate the lower relay, which will close the circuit between pin 5 (IGN) and your fuel pump. Therefore pump should fire up.

The IGN, during the start phase, will also be active and this will provide 12v at pin 1 and it is earthed through pin 3.. and this will activate the top relay and complete the circuit between pin 7 (+BAT) and pin 6 (ECM).

So, there should be no 5v anywhere. It should be +12v (battery voltage).

If you are only getting 5v from the ST SWITCH then you have a bad connection (ie high resistance) coming in from the ST SWITCH. 5V probably not enough to activate the relay and if so you wont get the fuel pump running.

After ST SWITCH has been done (2 secs) then power to run the fuel pump relay is coming from pin 6 (ECM). If this is not 12v then again it may not have enough volts to activate the pump relay (lower relay). The actual connection to run the fuel pump comes from IGN. That is ECM powers the relay and the contacts (when closed) run the fuel pump via IGN - after the 2 sec from ST SWITCH.

I'd be looking to see if you are getting 12v into pin 5 (IGN) as well as pin 2 (ST SWITCH) as a starting point. If not then trace back to find if theres a bad connection from those two sources.

During ST SWITCH (2 secs) you should have a good earth (ie zero resistance) between earth and pin 1 (ECM).

The above assumes you are supposed to be getting 12v.


But... if you are only generating 5V, and that's all it's supposed to supply, and your main relay (as per your picture above) is a 12V unit....

The voltage coming in is supposed to be 5V only, either from IGN (pin 5) and/or ST SWITCH (pin 2), and the relay you have is a 12v unit, then you need wire in a 5V relay for these inputs. Connect one end of the coil on the 5V relay to IGN and the other end to earth. So when IGN is active it will trigger your 5V relay. Connect one end of the relay switch side (on the 5V relay) to +12v and the other end into pin 5 (IGN) of your main relay. This will supply 12v to the big relay into pin 5 (IGN). Do the same for ST SWITCH to feed 12v into pin 2 of your main relay. Basically what this does is activate the 5V relay from your 5V source to switch in 12V into your main relay.

seeyuzz
river