Recent content by Tim Metford

Hi George, I've been busy with other things the last few days - like doing my share of the housework instead of playing around with pieces of wire and resistors! Here's a link to a site that seems to have a different take on how a timer might be constructed...

Ah! I see, I'll have another go at the circuit - it's my novice status showing me up here! Thanks for your patience.

Hi Fleck and I trust you are well. I've studied your posts and simulated your circuit as best I can (see below). The closest I can get to a 4020 in the Circuit Wizard simulator is the 4024 which is, I think, pretty similar to the 4020 except it's a 7-stage counter; and even then the Circuit...

Hi Guys! great job on the circuit and it's going to take me a day to work through all your posts! I'll assemble a circuit that, hopefully, will reproduce your work using component values as close as I can get to your spec on circuit wizard. I'd be so excited to see how this goes.

Really sorry to have mislead you there guys!! Oooops! - all embarrassed now! :rolleyes: - I hadn't realised I'd confused things by mentioning the lamp - don't know what I was thinking at the time! I hope you're okay with the description I've given about a room heater needing to switch itself...

Just to be clear about what I want to achieve: A room heater (a simple resistive load of ~3kW) needs to switch on for a period of approx 1 hour and then switch itself off and stay off until the next time I give it a signal current to turn on again. Because this room heater is at my office 13...

Okay, I'll see if I can piece this new info together but I'd need one of your magic circuits diagrams :confused: if poss please? and I hope I haven't confused things by not giving a simple explanation of what I need to be able to do.....

Good morning George! I trust you're feeling better? Yes, the manual switch causes the relay to be switched off - obviously this shows that if the 4020 sends Q14 high enough they will switch off the relay as intended. This bit, though, doesnt happen. I've tried various outputs from the 4020 -...

I've searched youtube and found this link that seems to do the sort of thing I'm looking for. this looks a bit beyond me at the moment!

Ah! yes, it does, when I bridge the 12V rail and the base of the 557's. I guess that extra volt (12..22 - 11.34) is sufficient to turn off the 557's?

Hi Fleck, sorry for the delay in getting back to you. With LED's and 150Ώ to several outputs including Q14 (which is the one I've connected to the the 557's) All of them start flashing as soon as I apply power to the 12V rail. As suggested, I've removed the 1k's from the bases of the 557's and...

Hi Fleck, thanks for letting me know how to use output 1 to show that the 4020 is counting. With reference to the BC547, it's there because, without it, the relay didn't seem to have enough power to operate so, I appreciate that this is overkill but please bear with me on this one until I get to...

I'll check this out too soon, but first I want to get this 4020 working if poss.

Ah!, okay, I notice your earlier wiring diagram for the 555 shows pin 7 connected to the 12V rail via a 4.55M resistor. I would've followed that had it not been for Fleck's diagram that shows it to be unconnected (as is pin 5 on his diagram too).

Thanks for the amendments and, as you can see from the diagram below, I've put the relay back in for the time being (I like to hear something go click, I think!). As for the circuit, Fleck, you were right the 557 had blown and, since applying your suggestions, that part of the circuit works but...