login
muckleluck
-
Posts
15 -
Joined
-
Last visited
Never
Content Type
Profiles
Forums
Events
Posts posted by muckleluck
-
-
sweet. thanks for the help guys.
-
I decided to us an astable 555 timer circuit with a 1M ohm pot and a 100 microF cap to (hopefully) give me the correct timing range. What I can't figure out is which transistor to use to switch the current to the lamp. Does anyone have any suggestions? I might need to switch up to 8A. Am I on the right track with this or is there an easier way?
-
I need to build a light flasher to test brake lights in cars. The input voltage is 14V and the max current about 3A. The light needs to be powered for 30s-1min (adjustable whether by a switch or a pot doesn't matter) and then off for 30s-1 min. Anybody have any suggestions for a simple circuit that can meet these specifications?
Muckleluck -
Ok I got it to work now on my breadboard. When I eventually put it together permanently I am going to connect a 7805 so that I have a fixed supply and a variable all in one unit. What should I use for a heat sink on the 7805 and the LM317?
Muckleluck -
I bought the transformer specifically for the project. It is rated 24 VA so that is more than enough for this circuit I think. The only current that I am trying to draw is whatever the 7408 requires with just the power connected.
-
If someone has a similar supply taht works I can only assume that I have assembled something incorrectly. I'll take a careful look at it and if all else fails start again. Thanks.
Muckleluck -
Hi,
I don't know if someone already covered my problem in a previous reply but I too am having a problem with a power supply that I built based on the LM317. The schematic can be found at:
http://www.uoguelph.ca/~antoon/circ/vps.htm
My circuit is identical to this one except I haven't installed the voltmeter or the led branches. When I connect it to a 7408 TTL chip the voltage drops from 5V to 2.3V. In the construction section the author suggests adding two diodes to drop the min output voltage to zero. I found that the voltage went to 0 without them so maybe that is a problem? -
With this arrangement the chip is acting like a NOR gate. If I reverse the connections so that the resistors are connected to the ground and the switches to the V+ the led will never turn off because the pins float high. Thanks for bearing with me on this line of basic questions - this is the result of a the elec education they give mech eng students.
Muckleluck -
Yeah it seems to be a power supply problem. I have another question about these chips. I want the inputs to be low normally and high when I press a button. How can I achieve this?
Muckleluck -
I'm messing around with some logic gates trying to get a basic understanding or digital logic but for some reason I can't seem to get them to work. The specific chip that I am using is a 7408 TTL AND gate. For some reason when I connect the power to the chip the voltage drops from 5 to 2.3. I can't figure out whether I have a power supply problem or I'm doing something wrong with the set up. If anyone has an idea of whats going on your help would be appreciated.
Long delay light flasher
in Electronic Projects Design/Ideas
Posted
Oh wait... so you mean I should use a transistor and a power mosfet or can I drive the mosfet directly with the timer output?