any electronics genius?

[unxetas]

Hi guys..

I'm trying to build this intervalometer http://www.twistedeyes.com/intervalometer.pdf but I'm not having much success :S

I wired everything like the schematics and right now when I flip the switch, the led comes up (after several seconds up to a couple minutes..) but it remains lit instead of flashing..

The relay doesn't click, it's a 16v 10A relay.. I guess it should work :S and I'm guessing that's also why the led stays up.. I think the output from the relay which is going into the IC would "trigger" the IC.. ??

Any help at all you can give me would be appreciated.. what should I check?

Thanks a lot guys, really hope you can get me going on this one

Tiago Santos

[Juno]

Sometimes they show up on e bay for a good price. If you can find one it may save you a lot of time and effort.

[Actor]

The relay doesn't click, it's a 16v 10A relay..

When you say 16v 10A is this the coil or the contacts? My guess that you have a 16v coil with 10A contacts. i.e., it takes 16v to pull in the armature, which will carry up to 10A.

What is your battery voltage? To pull in a relay with a 16v coil you will need at least a 16v battery. The 555 is rated at 18v so don't go any higher than that.

I wish there was a real schematic instead of this drawing.The drawing appears to be "dead bug" POV, i.e., the pins of the IC pointing up at the viewer as the chip lays on its label side. If this is so then the pin at the lower right is pin#1. The rest of the pins are numbered counterclockwise from pin#1. Pins#1 to #4 are on the bottom row numbered from right to left. Pins#4 to #8 are on the top row numbered from left to right. The pin at the top right is pin#8.

Anyway, the author is most likely trying to describe an astable multivibrator. Unless he has come up with a working circuit the likes of which I have never seen before, the drawing is all wrong. Here is a link to a correct schematic:

http://courses.ncsu.edu:8020/ece480/com ... 80_555.htm

Note that this correct schematic has two LEDs. One is between the output (pin#3) and Vcc. The other is between the output and ground. One will be on while the other is off. The coil of your output relay should be in parallel to one or the other of these. I prefer to put the coil between pin#3 and ground.

One other thing. The 555 is not designed to handle inductive loads such as relay coils. Since your load is a relay coil you need to put a diode between pin#3 and the coil, with the cathode end connected to the coil. Another diode should be connected in parallel with the coil, with its cathode connected to the same end of the coil as the other diode.

The problem with coils is back EMF. When voltage is removed from the coil the magnetic field around it collapses and for an instant it becomes a generator. The first diode allows current to reach the coil when pin#3 is high but prevent current from the back EMF from entering the IC. The second diode short circuits the coil as the field collapses.

As for which end of the diode is the cathode, look at the packaging. It should tell you how to identify which end is the cathode and which is the anode.

[danpuddick]

this isn't very helpful, but... in the next issue of the magazine that this article comes from there is a correction for the building of the intervalometer. I remember as I downloaded it before. But then some happy chap stole my computer so I can't remember where I down loaded the article from. But I'm sure you know where you got it from and there are the other projects from the magazine. So take a look in the one for the month after.

good luck

[unxetas]

well I got this pdf from someone else, I'll try to ask him about the correction but...

thanks for all the replys, specially the one with the working circuit..

as for the coil, my bad, it's a 12v 10A.. I have a 9v bat but it should work since I tried running some wire from the battery straight to the relay and it clicked.. now whether the power coming out of the IC is enough.. beats me :S

[unxetas]

well I found the correction! I'm not sure if it's ok to post the link here (copyright?), as it contains scans of most Super 8 Filmmaker issues.. not full issues though! It's a pretty nice resource, let me know if I should post it or not..

[Actor]

I have a 9v bat but it should work since I tried running some wire from the battery straight to the relay and it clicked.. now whether the power coming out of the IC is enough.. beats me

I don't think there is enough power coming out of the IC. The literature says that when the output is high it should be the same as Vcc, but in my experience that has never been the case. There is always some voltage drop, how much I don't know.

I built a circuit like this for time lapse day. I used a 9 volt relay and a 9 volt battery. It did not work. Using two 9 volt batteries in series solved the problem. Of course I may be slowly destroying the relay but so far, so good.

[Alex]

well I found the correction! I'm not sure if it's ok to post the link here (copyright?), as it contains scans of most Super 8 Filmmaker issues.. not full issues though! It's a pretty nice resource, let me know if I should post it or not..

I've actually made contact with two people from Super-8 filmmaker magazine. They don't seem to possessive about their mag.

Too bad actually.

[MovieStuff]

I have a 9v bat but it should work since I tried running some wire from the battery straight to the relay and it clicked.. now whether the power coming out of the IC is enough.. beats me

I
I built a circuit like this for time lapse day. I used a 9 volt relay and a 9 volt battery. It did not work. Using two 9 volt batteries in series solved the problem. Of course I may be slowly destroying the relay but so far, so good.

Why not just use a 5V relay? Board mounted 5v relays are pretty common and very cheap. After the slight DC drop coming off the circuit, 5v relays work like a charm on a circuit that uses a single 9v battery. However, I generally use two 9v batteries in parallel, just to provide more amperage to the coils and make the power supply last longer.

Roger

[daddysauce]

unxetas

I tried this PDF about a year ago. Save yourself the grief and get a MK-111 relay unit from Maplins. All the work is done for you.

[Actor]

I have a 9v bat but it should work since I tried running some wire from the battery straight to the relay and it clicked.. now whether the power coming out of the IC is enough.. beats me

I built a circuit like this for time lapse day. I used a 9 volt relay and a 9 volt battery. It did not work. Using two 9 volt batteries in series solved the problem. Of course I may be slowly destroying the relay but so far, so good.

Why not just use a 5V relay?

I just happened to have the 9V relay on hand, plus it was late at night and Radio Shack was closed. I also had an extra 9V battery snap on connector. RS sells these in packages of in bundles of a half dozen or so. Wiring in another battery was the quickest, easiest thing to try. I did not have an extra 9V battery so for test purposes I robbed the 9 volt battery from our smoke detector, putting it back immediately after verifying that the circuit worked. (The smoke detector has saved my life before.)

If upping the voltage had not worked then a 5V relay would have been my next approach but that would have had to wait until the next day. Replacing the relay would have been more work, unsoldering the old and soldering in the new. As it is the present circuit works and I'm of the "if it ain't broke, don't fix it" school.

[Actor]

unxetas

I tried this PDF about a year ago. Save yourself the grief and get a MK-111 relay unit from Maplins. All the work is done for you.

I agree. I would have done that myself had I known they existed.

[unxetas]

well, there is no Maplins in Portugal and.. what do you know, the corrected Super 8 filmmaker schematic works like a charm

after having the correct drawing, it took me less than an hour to build the thing, it worked first try!

btw, the voltage coming out of the IC is Vcc less 1.7V, so in this case, 7.3V.. it's apparently enough to "click" a 12v relay, unless with all the soldering my relay got "special"

I'm posting the correct circuit here, if anyone has any problems with this, please let me know.. I'll edit it out or ask a moderator to delete it!

http://www.super8mm.org/pdf/v7n5.pdf

I didn't have a 0.1mfd capacitor at hand so I just left the control voltage pin untouched.. it still works..

As a somewhat rough estimate, I think I have a variable intervalometer from about 5fps to almost 1 frame every hour (actually 3300 seconds or so..)