I have some uA2240cn timer chips, which I purchased hoping to use them as easily as the trusted old 555s that I have always used.
Alas the info on them in the only datasheet I can find is slightly beyond my limited understanding of electronics and to be honest I don't have the slightest idea of how they work, and I can't find a single schematic on the net that uses them.
I was hoping to build a couple of timers, one is simply a monostable to delay turning on a relay by about 20 minutes, and the other I need is an astable that will turn on a relay for between 3 to 10 minutes and then off for between 2 to 5 minutes repeatedly. The latter is for some disco lighting that depending on the surrounding temp, overheats if run constantly!
If anyone would take pity on me and help to design these circuits or help me to understand the basic workings of the uA2240cn I would be most beholding to them. I am not a complete novice with electronics but have been out of the game for 20 odd years and just seem it harder and harder to take things in nowadays
Anyway thanks for looking and keep up the excellent forum!
I thought the 2240 looked familiar. I found a complete chapter in one of my old text books about the EXAR XR-2240. It really dates me I graduated from college in 1981 and the text book was published in 1977. But I would be glad to read up on this IC and give some help.
Here is a design for the 20 minute delay to turn on a relay. From what I can figgure out when the power is applied the 2240 automatically powers up in the reset mode and all the outputs are a logic level 0. The CD4103 (dual D F/F) latches to on to the time delay set by the timiming rc on pin 12 of the 2240. The rc connected to pin 4 of the 4013 is to insure the Q output is low in power up.
Hope this helps
Here is a design for the 20 minute delay to turn on a relay. From what I can figgure out when the power is applied the 2240 automatically powers up in the reset mode and all the outputs are a logic level 0. The CD4103 (dual D F/F) latches to on to the time delay set by the timiming rc on pin 12 of the 2240. The rc connected to pin 4 of the 4013 is to insure the Q output is low in power up.
Hope this helps
Yes I have posted a 2240 to you, it should arrive tomorrow (thursday) with any luck, sent it first class today, so if the GPO is on form and not on strike, you could be timing very shortly!
Here is the circuit for the double time. I am using the fact the on power up or when reset the output of the 2240 to at logic level 0 to turn on the PNP transistor. If you need adjustable times use a similar circuit that I posted earlier.
This circuit will give a 20 minute delay before energising the relay, after the 'Trig p/b is pressed'.
This should cover project number one of your thread for the original post.
I'll post the ON/OFF timer sequence later.
BTW, your HCF4013 are not 'D type F/F's', check the datasheet. EDITED: download 3 different datasheets for the HCF, two say its a gate and one says its a F/F...??
Let me know when you have the circuit working, it works on my test bench OK.
PS: you didnt include a return address in your package, so that I can send the ic back.
Just thought I would let everyone who helped me with this problem know that at last I have working timer circuits, and its a very handy timer at that now.
Special thanks to K7elp60 and Eric Gibbs, who both put time and effort into helping a noob for no other reason than being good blokes.
I can't thank you enough and hope one day I can return the help.
Just thought I would let everyone who helped me with this problem know that at last I have working timer circuits, and its a very handy timer at that now.
Special thanks to K7elp60 and Eric Gibbs, who both put time and effort into helping a noob for no other reason than being good blokes.
I can't thank you enough and hope one day I can return the help.