I have a circuit using the NE555 wired in the typical astable operation. I am using ~6.1V input (Vdd). However my ouptput square wave is measuring 3.2V. I need the ouput square wave to be at least 5V.
What is causing this and what can I do to correct this problem?
FWIW I also tried using ~12V input but I kept burning up chips. It seems to work fine with the lower volate but I am getting the unwanted voltage drop.
Thanks in advance.
Last edited by dwhitt; 8th July 2009 at 08:04 PM.
You probably have the output overloaded. Post a schematic of your whole circuit.
Lions and tigers and bears, OH MY!
Thanks. I only have a hand drawn one at the moment but will try to come up with something to post before I leave today.
See if this works. I did this quickly and please keep in mind that drawing electrical schematics are not part of my job so forgive me if I got a symbol wrong.
The switch is actually a double pole double throw switch but the second switch is practically independent with its own power supply. The output of the relay is also on that second schematic.
I'm not sure what information you may need on the counter/timer. If you have specific questions let me know and I can look it up for you. Thanks again.
Last edited by dwhitt; 8th July 2009 at 07:36 PM.
The output of a NE555 (Fairchild Version) is rated at 100mA output at 5 volts, however at this output the voltage is down to 3.3 volts. Sounds like you have more than 100mA load on your output. The coil resistance of your relay need to be greater than ~100 ohms for a 5 volt relay.
Right. You most likely need a transistor to drive the relay.
Lions and tigers and bears, OH MY!
Thanks for the inputs Brown and Bailey. Just to clarify... I need to put in a transistor between the output of the NE555 and the relay?
Yep, that is correctOriginally Posted by dwhitt
Something like this could get you started, assuming that the relay is small
Lions and tigers and bears, OH MY!
The TTL version is rated to 200mA, the CMOS version is rated to 100mA and that depends on the supply voltage.
What's connected to the output of the 555?
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The relay is a Magnecraft W6225DSX-1. I don't see anything from the packaging that tells me the coil resistance? These are the specs they gave me:
The NE555 I have is (don't laugh) a radio shack brand chip (TLC555 Timer). High output current capacity Sink: 100 mA (typ) and Source: 10mA (Typ).
- Solid State Panel Mount Relay
- Control Voltage Type: DC
- Load Current RMS Max: 25A
- Contacts: SPST-NO
- Control Voltage Max: 32V
- Control Voltage Min: 3V
- Output Current: 25A
- Output Device: SCR
- Output Type: SCR
- Output Voltage: 280VAC
- RoHS Compliant: YES
So this is what I purchased today- two NPN Silicon Transistor: one with an Ic of 3A and the other with 10A.
Please advise which transistor would be best and also please take a look at my updated schematic to see if this *Should* work. TIA.
I did't realize you were using a SS relay. Accordig to the data sheet, the input resistrance should be 1500 ohms, minimum. You're timer should be capable of driving that directly, unless I'm missing something.
Try disconnecting the relay and measuring the output of the timer. Maybe something else is going on.
Lions and tigers and bears, OH MY!
OK. I will try disconnecting the relay, measuring the output.
Then connect doing the same with the timer. I will hold off on the transistor for now and report back.
hi,
Your circuit will not work as expected also the freq of the 555 is 75Hz, the relay will buzz.!
Eric " Good enough is Perfect "
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Can you please elaborate on this? I am not sure I am understanding?
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