Need help building delay circuit to run SPDT relay

Phil-S

Joined Dec 4, 2015
238
I have a collection of my father's tools (cabinet maker and craftsman) including some very large cast steel chisels.
No man in one lifetime could ever wear these down. They are sods to sharpen - one minute edge chip is an hour's worth of cold grinding.
Kids don't want this stuff now, but it would break my heart if they ended up in landfill - I would rather burn them.
I worked for a large utility that threw out stuff rather than re-stock it - skiploads of phones, IBM Golfball typewriters, monitors
As a result, I too have an endless supply of things like cable ties, a phone for every socket, etc., etc, which will end up in landfill.
Going back to the OP, is this a bit of whimsy, or does it have a serious purpose?
I have a simple rule of thumb - more than one relay, more than one timer = MCU.
I got into MCU's (Arduino) late in life - now every problem gets an MCU. 3-years to get reliable counts back from a gas meter via Hall sensors, Zigbee networks. It beats religion hands down.
An AtTiny would do all of this.
 

Thread Starter

richsoucie

Joined Jan 8, 2016
19
It is to split the running light and turn signal that are on a single + now. It will in theory split it so the running lights have a separate + than the turn signal
 

Phil-S

Joined Dec 4, 2015
238
A small MCU - AtTiny85 for example, would let you do all you want here. It would have the ability to monitor voltages on different lines then output to separate relays or whatever. Where it really scores is that you get easy, precise timers and changes to the configuration can be done in software rather than rewiring everything - ten second delay is delay(10000), 15 second is delay(15000) - all done in milliseconds.
 

Tonyr1084

Joined Sep 24, 2015
7,853
After a whole lot of reading and failing to understand exactly what it is you're doing and why, I've hunted down a circuit I built a few years ago.

History (of my circuit and need): I have two panel meters that can be lit in colors to match the interior dash lights. Once you set a color they remember the setting. However, nearly every time I started the truck the meter lights would come on. For that instant, the power drain during starting would cause the color to default to the original color. I had to set the color I desired every time I started the truck. So I, too, wanted to delay the time they came on. So I devised this simple RC circuit (below)(hopefully). (I'm new to this forum and might have difficulty posting the picture, so if I fail, don't nobody blast me out of the water over it).

The circuit consists of a 24 volt dc relay (YES, 24 VOLT) (scrapped out of an old dishwasher control board). When power comes on R1 begins filling up C1. When C1 reaches sufficient voltage, current at the base of Q1 begins to turn on. As its voltage rises closer and closer to 13.8 volts (normal positive auto voltage) the relay would click in. Once it does, D1 becomes active and provides full power to the relay, thus, holding the relay locked on until I switch off the engine.

I've been using this circuit these past few years with no problem. The meters come on approximately four seconds after I start the truck. Differing values will result in differing time delays. I don't know if this suits what you wish to do but I hope this at least puts you on track for what you are attempting to do.

Good luck.Time Delay Start.png
 

Phil-S

Joined Dec 4, 2015
238
Nice drawing - how did you do it?
Sorry to drone on about MCU's
Even the smallest MCU's have non-volatile memory (EEPROM), sufficient to retain for years any values you want to use after power-off.
I a relative newcomer to the Atmel/Arduino phenomenon, and there is a huge learning barrier to get over, but now I look for practical uses for them around the house etc. My main aim is to do energy management and monitoring. It has taken about three years to get results back from a gas meter to inside the house, but it is very satisfying to see how much energy you are using, how the boiler behaves, how insulation affects consumption. Once you have cracked one meter, the rest are easy-ish. For what you get in terms of technology, these devices are dirt cheap - £3 each for loads of digitals, analogues, memory. You can essentially wire everything up then "connect" in software. Where they aways score over analogue circuits is that you can forget the vagaries of +-20% capacitors and just write the time you want.
Good luck
 

Phil-S

Joined Dec 4, 2015
238
Hello
I admire the dedication to this, but the objective still eludes me.
That aside, the electrics of motor vehicles are a very hostile environment to work in.
12-V nominal, but with all sorts of spikes, surges, anything up to 60-V, plus dropouts.
Many components (regulators are a good example) come in automotive grades, specifically to overcome the sort of noise that kills most commercial components.
My suggestion would be to protect your circuit with large (4700uF) capacitors to get some smoothing, a decent 12-V or 5-V automotive grade regulator, decouple all your IC's right at the Vcc and GND pins (10uF + 0.1uF caps), diodes across relay coils.
A scope across power supplies might reveal what is going on. If your circuit works on the bench away from the vehicle, it will work in the vehicle if you protect it enough. What you are trying to do is simple enough, but just needs beefing up. A word of warning though - if you let relays chatter long enough, you are going to do some serious damage somewhere , like the EMU.
 

Thread Starter

richsoucie

Joined Jan 8, 2016
19
It does work in the vehicle in run with engine off the chatter only happens when the engine is running. There is no flicker on a bulb connected in place of the relay coil but when the relay is connected it gets slight chatter and then latches is ot possible that the 555 is not providing enough current on pin 3 to activate the relay
 

Phil-S

Joined Dec 4, 2015
238
I'm not surprised at what you have seen. Looking at a lamp flickering is not a good indication of what is going on, especially an incandescent type. Even a relay is fast enough to pick up dropouts etc.Clean up the voltage supply and protect the output of devices. You are working in an electrically noisy environment. If you have fuel injection, there will be fuel control solenoids potentially putting spikes on the power lines, and so on.
It is generally good practice to run relays through transistors when controlled by "chips" of any sort. Running relays directly from "chip" outputs is asking for trouble. Find out what the relay coil inrush current is (should be less than 1-amp) and match it to a suitable transistor. Use NPN if the IC output is active high or PNP for active low. 2N3904 and 2N3906 are examples of both types and are good for 12-V systems and will take up to 100-mA. Use higher power versions if necessary. Use 1-k to 10-k resistor on base
 

Thread Starter

richsoucie

Joined Jan 8, 2016
19

its working now the chip wont supply supply enough current to pull the relay cleanly at 14v which is the output when the vehicle is running
 

Phil-S

Joined Dec 4, 2015
238
Well done.
I would still advise driving the relay(s) through a transistor rather than directly off the IC - it's safer and better practice.
Do you really need that 50-W resistor? Which version of the 555 is it? If it's the LM555, it has a recommended max supply voltage of 18-V - you could easily get over that as spikes. If you want to make this "permanent", stick a robust low dropout regulator on the front end - Texas or Microchip do the automotive grade devices which are almost bomb-proof and specifically designed for vehicle electrics.
 

Thread Starter

richsoucie

Joined Jan 8, 2016
19
The resistor is required because the body control module checks the circuit for load of an incandescent bulb if it is not present it will.cut the power to the turn/running lights wire. That line is regulated to run at 13.8v by the cars computer so voltage spikes should not be an issue. It is ne555p
 

Phil-S

Joined Dec 4, 2015
238
The alternator output is regulated by the diode/regulator pack fitted to the alternator - it designed to provide a rough DC voltage of about 13.8-V which is the optimum charge voltage for a six cell lead acid battery - it does not remove dropouts due to cranking the engine or spikes due to other components - the engine management unit - "computer" - does not control the line voltage as it does not feed back to the regulator. The battery will provide some voltage stabilisation, but it is not a capacitor. There are general rules in place when dealing with IC's and decoupling and a stable supply are taken for granted. You increase the chances of things working by adding these simple things.
The NE555 is an old design and has been largely superceded by 7555's and the like.
If it all works for you, then that's OK.
 

Thread Starter

richsoucie

Joined Jan 8, 2016
19
There is a seperate computer that controls all the lights the gauge cluster basically everything except the engine. It has a circuit to detect load on the circuit and cut power if no load is present and it is a logic controller certain conditions must be met to activate the daytime running lights and there is no way to disable them so i cant imagine it not being regulated. All power to everything in the car except the starter circuit is cut before the starter engages which also causes a loading issue with my android radio(but thats a different matter completely) everything in this car is computer controlled including the throttle its a big pia
 
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