False triggering of a 555 timer

audioguru · Mar 13, 2017

Google does not know about a "mall rectangular", 9V, E style battery. I think the problems are caused by the battery or LM317 being overloaded by the high starting current of the pump.
You can add some "power up reset" parts to fix the timer triggering on power up problem and maybe a capacitor larger than the 1uF at the output of the LM317 to fix the timer triggering when the switch is used problem.

jacbk6121 · Mar 13, 2017

audioguru said:
Google does not know about a "mall rectangular", 9V, E style battery. I think the problems are caused by the battery or LM317 being overloaded by the high starting current of the pump.
You can add some "power up reset" parts to fix the timer triggering on power up problem and maybe a capacitor larger than the 1uF at the output of the LM317 to fix the timer triggering when the switch is used problem.

Thanks. I attached a picture of the 9V battery. I understand what you are getting at. Not sure what you mean by "power up reset" parts, can you be more specific.
I already have a 220 uF cap between the output of the LM317 and ground, do you mean putting a 1uF between pin 2 (Vout) and pin 1 (ADJ)?

Cheers,

Jacques

audioguru · Mar 13, 2017

That is your problem! You show a photo of a weak ordinary little 9V battery that probably "falls flat on its face" (its voltage drops very low) when it is overloaded by the high starting current of the pump. Use a much larger battery (six AA or D alkaline cells?).
Also, in my post #9 I mentioned the wrong connection of your capacitor parallel to the 240 ohm resistor on the LM317.

Pin 4 on a 555 resets it when it is at a low voltage. If you connect a discharged capacitor to ground on pin 4 then the 555 is reset during power up, then add a resistor to slowly charge the capacitor and activate the 555 after power up. A 47uF capacitor and 10k resistor will produce a power up reset time of 47uF x 10k= 470ms which is almost half a second.

jacbk6121 · Mar 13, 2017

audioguru said:
That is your problem! You show a photo of a weak ordinary little 9V battery that probably "falls flat on its face" (its voltage drops very low) when it is overloaded by the high starting current of the pump. Use a much larger battery (six AA or D alkaline cells?).
Also, in my post #9 I mentioned the wrong connection of your capacitor parallel to the 240 ohm resistor on the LM317.

Pin 4 on a 555 resets it when it is at a low voltage. If you connect a discharged capacitor to ground on pin 4 then the 555 is reset during power up, then add a resistor to slowly charge the capacitor and activate the 555 after power up. A 47uF capacitor and 10k resistor will produce a power up reset time of 47uF x 10k= 470ms which is almost half a second.

The voltage on a new battery usually falls to about 8.2. Unfortunately I do not have more room for a bigger battery. I have tried (2) 9V in parallel at one point and this did not help.

I don't know where post #9 is or I would look it up. Here a revised schematic with your pin 4 recommendation.

alec_t · Mar 13, 2017

You could try decoupling the +ve supply to the timer, like this :

D2,C2 hold the voltage up when the motor start-up current tries to drag it down.

jacbk6121 · Mar 13, 2017

audioguru said:
That is your problem! You show a photo of a weak ordinary little 9V battery that probably "falls flat on its face" (its voltage drops very low) when it is overloaded by the high starting current of the pump. Use a much larger battery (six AA or D alkaline cells?).
Also, in my post #9 I mentioned the wrong connection of your capacitor parallel to the 240 ohm resistor on the LM317.

Pin 4 on a 555 resets it when it is at a low voltage. If you connect a discharged capacitor to ground on pin 4 then the 555 is reset during power up, then add a resistor to slowly charge the capacitor and activate the 555 after power up. A 47uF capacitor and 10k resistor will produce a power up reset time of 47uF x 10k= 470ms which is almost half a second.

Just tried the cap. on pin 4 , no help.

jacbk6121 · Mar 13, 2017

alec_t said:
You could try decoupling the +ve supply to the timer, like this :
View attachment 104917
D2,C2 hold the voltage up when the motor start-up current tries to drag it down.

Just tried it, no help.

aardyvarky · Mar 13, 2017

jac, could you measure the current the motor draws as it is running?

audioguru · Mar 13, 2017

jacbk6121 said:
Just tried the cap. on pin 4 , no help.

1) Disconnect pin 4 from anything else like away from pin 8.
2) Add the 10uF capacitor from pin 4 to 0V (ground) which is at pin 1.
3) Add the 10k resistor from pin4 and the capacitor connection to the positive supply which is pin 8.
They the circuit will have half a second of power up reset.

jacbk6121 · Mar 14, 2017

aardyvarky said:
jac, could you measure the current the motor draws as it is running?

It is using 150 mA at 4.7V

jacbk6121 · Mar 14, 2017

audioguru said:
1) Disconnect pin 4 from anything else like away from pin 8.
2) Add the 10uF capacitor from pin 4 to 0V (ground) which is at pin 1.
3) Add the 10k resistor from pin4 and the capacitor connection to the positive supply which is pin 8.
They the circuit will have half a second of power up reset.

Yes, I have tied this.

aardyvarky · Mar 14, 2017

Try this:

TIP110 won't need a heatsink at 150mA, the 27R resistor charges up the 220uF cap to ~9v, which should be enough energy to get the motor running, then Vmotor drops to 5v (if motor runs too fast, recalculate 27R resistor).

jacbk6121 · Mar 14, 2017

aardyvarky said:
Try this:
View attachment 104933
TIP110 won't need a heatsink at 150mA, the 27R resistor charges up the 220uF cap to ~9v, which should be enough energy to get the motor running, then Vmotor drops to 5v (if motor runs too fast, recalculate 27R resistor).

OK, I'll give it a shot

jacbk6121 · Mar 14, 2017

jacbk6121 said:
OK, I'll give it a shot

Just to be clear what is the TIP110?, is that just nomenclature or a different transistor and if so what exactly is it?

Jacques

aardyvarky · Mar 14, 2017

I forgot to mention that the red line in my drawing is +9v.
https://www.ebay.co.uk/itm/TIP110-Trans-Darlington-NPN-60V-2A-3-Pin-TO-220-/291750394708?hash=item43edadbb54:g:JVoAAOSwr41XIgEv
TIP110 is an NPN darlington transistor - any with HFE of 1000 and 2A min will do e.g. TIP120,121 or 122

audioguru · Mar 14, 2017

Since the power up reset does not work then increase its duration by increasing the 10k resistor on pin 4 to 100k .

I found the datasheet of a 9V Chinese "super heavy duty" old style battery. A brand new one can barely provide 40mA and your pump draws much higher starting current.
The LM317 needs a minimum input that is about 7V but the cheap little 9V battery voltage will be much lower. A modern alkaline battery or a much newer Lithium battery might work.

jacbk6121 · Mar 14, 2017

aardyvarky said:
I forgot to mention that the red line in my drawing is +9v.
https://www.ebay.co.uk/itm/TIP110-Trans-Darlington-NPN-60V-2A-3-Pin-TO-220-/291750394708?hash=item43edadbb54:g:JVoAAOSwr41XIgEv
TIP110 is an NPN darlington transistor - any with HFE of 1000 and 2A min will do e.g. TIP120,121 or 122

OK, I will have to order this, it may take a week or so for delivery. I have a PN2222A transistor but I don't think it will do the job.

aardyvarky · Mar 14, 2017

Try the 2N2222A before you buy anything else, a 555 should source plenty of current. However, refer to Audioguru's comment about the battery - here (UK) we have 9v batteries in the shape of "PP3" and a good quality one has plenty of power - I just tried one (an Energizer) on a 6v motor. Just out of interest, what are you pumping?

alec_t · Mar 14, 2017

aardyvarky said:
we have 9v batteries in the shape of "PP3" and a good quality one has plenty of power

.... but not for long. PP3 capacity is only ~500mAh, so a pump current of 150mA would flatten the battery in ~ 3hrs or less.

audioguru · Mar 14, 2017

alec_t said:
.... but not for long. PP3 capacity is only ~500mAh, so a pump current of 150mA would flatten the battery in ~ 3hrs or less.

But the important problem is that the battery voltage drops so fast that the LM317 regulator does not work.

False triggering of a 555 timer

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