Hi, hey I was just curious if anyone can post or direct me to a timer circuit that uses capacitors that discharge in sequence to make leds flash, preferebly quite slowly, like (one onthousand *FLASH* two onthousand *FLASH* Three onethousand *FLASH*, etc.)? Here is the catch....I want to do this using no digital logic chips or transistors, only caps, resistors and, relays. I have already made a circuit that does this except that the leds flash really fast, too fast. Let me know...

I have a fasination with electro/mechanical gadgets, like any electronic device pre 1950, or before transistors. I guess I like it cause you can see everything happening and not being hidden inside the components of modern digital electronics. Plus I am trying to get a better handle on my understanding of things like electronics, and boolean logic. I figured for me, one of the best ways to learn would be by going backwards and messing with relays, and so I have a ton of mini 2.8 v relays. I also have been collecting old / antique electronic books. Id really like to mess with vaccume tubes as well, but that might be down the road a bit...I really dont want to electrocute myself with 150 vDC, not right yet anyway.

Thanks in advance.

Bart

 

Have you tried putting a large value of capacitor in parallel with the relay coil to slow down the energizing time? You could do that and daisy chain a bunch of relays. Once on turns on have it's contacts energize the next and so on.

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Yes, that is essentually how I originally made the circuit I have been messing with...It works, but still the leds flash really, really fast (even with a 2200uf cap) unless, mabe I dont have it wired together correctly, or need many caps in parrellel....I got the idea from a circuit I found online, however the relays in the circuit I found have many outputs, mine only have two, one (on) when not energised, one (on) when the relay is energised.

I was just thinking about this....I bet one way to do this would be to build some sort of logic with the relays, like a basic adder which wont let the next led flash untill like 10 loops of the daisy chain as you put it....Or then again, mabe not...building an adder/flasher with just relays would probably take like 20 relays or somthing....

 

You need a resistor in series with the relay coil and a cap across the coil.

This will slow both the operate and release times.

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Len

 

I started in electronics by building valve (or vacuum tubes as you call them) circuits. The secret to handling high voltages is to never use two hands when working on live circuits. Thus you may receive a shock through the hand and it hurts, but it won't be fatal. But if you use two hands, the current may go through your body and could be fatal.

Also beware that some capacitors may remain charged even after the power is switched off. So it is a good idea to measure the cap voltages before handling. If charged, discharge them through a resistor, say 100 k.

Alternatively, if you have an analogue meter, you can use it to discharge the caps since they have a lower resistance than the modern digital meters.

In order to flash the LEDs, I suggest you use a relay counter driven by a relay oscillator.

I'll design one for you and post it tomorrow.

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Len

 

Actually, that isn't really true!.

A digital meter usually has a fixed input impedance of 10Mohms, this is the same on all voltage ranges. An old analogue meter has 'ohms per volt', the most common being 20,000 ohms per volt - so on the 1000V range (which you would probably be using on valve circuits), has an input impedance of 10Mohms - double that of a digital meter. On the 100V range it would be only 2Mohms, but that's probably too low a range?.

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Good point Nigel, I had not done the arithemetic. However, with an analogue meter, you can alter the range as the cap discharges and thus speed up the discharge rate.

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Len

 

Thanks for the info ljcox, I havent tried the resistor in series yet, that might just be the ticket. Just as a quick note, I thought of another way of creating a simple timer, almost purely mechanical. Picture this... a non-conductive cylendar that rotates slowly by way of a motor....along the cylendar are connecting points that contact comb like wires/connections which light the leds, each comb connection is isolated from each other. One of the earliest relay computers used this method as basicly a memory device that swithes the electricity on and off in a timed manor. I also saw somthing like this in an ancient pinball machine. Which you can see here...
http://imagehost.epier.com/2277/WinCir6.jpg Its that cylendar thing with the comb near the top of the photo. Actually I dont even know for sure that that is what it is....But its my best guess...Anyway, Its really simple and it works. The ancient pinball your looking at is here... http://imagehost.epier.com/2277/WinCir1.jpg

 

Yes a motor driven switch would work.

Here is the relay counter proposal that I mentioned above.

If you want me to fill in the resistor and capacitor values, I will need the data on the relays you intend to use.

Attached Images

Relay counter.gif (67.3 KB, 11 views)

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Len

 

Wow thanks ljcox, ya know you didnt have to go through all the trouble with that sketch but I really appriciate that you did...Well the relays I have are here.. Russian made, high quality relays RES-15...Control voltage is 2.8V 60mA. Switching voltage up to 150V 100mA. Thats all the info I have on them as I picked em up off ebay and the box they came in is written in Russian. 72 for about $21.00 USD which includes shipping, a good price I thought. Here is a link to them on ebay... http://cgi.ebay.com/Miniature-relay-...QQcmdZViewItem

 

These relays have a rather low coil resistance, ie. about 47 Ohm.

This means that C1 will have to be rather large unless you can find a relay with a higher resistance coil for relay A.

What supply voltage do you want to operate it from?

If you used say 3 Volt, then the B, N2 & N3 relays would have to be 2 relays with their coils in parallel. Or if you used 6 Volt, then the coils could be in series. But the N1 & N4 relays would need a 47 Ohm resistor is series with their coils.

The circuit as drawn is a Modulo 4 counter. I expect that you realise that you can increase or decrease this if you wish. For example if you want a Modulo 6 counter, then you would add 2 more sections like the N2 & N3 sections.

If you do a search of this forum you will find plenty of relay circuits. I've inserted a few myself.

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Len