monostable timer with a 555 ic - relay voltage

relay voltage

Hi gang.
I built a monostable timer with a 555 ic. The timmer will energize 2 spdt 5v relays. The 2 relays are connected together in parallel so they can be used for reversing a motor polarity.
Here is some info on the timer and relay:
Timer-
100uf capacitor and 22k resistor to give a 2.4 sec time

Relays-
5v
59 ohm coil resistance

When I first tested the timer circuit, I used a 9v transistor battery for the timer power. I hooked up a volt meter to the output and when the timer was triggered, I got a voltage at the output of about 8v. Timer worked great.
When I connected the relays to the output, the timer worked like a switch. Meaning one trigger relay on, trigger again, relay off.

When I used 5v for the timer supply, the timer and relays worked perfectly.

Can someone tell me why at higher voltage, the relays latched in the energized state?
Was the higher voltage going to the relays creating too much of a load for the timer to time out?
I know that my circuit is working great at the proper relay voltage but would like to know why it did what it did at the higher voltage.
Sorry for the long post.
Thanks in advance.
Bill

Re: relay voltage

gnomeman,
Your description is not clear to me. Can you supply a schematic?
Regards,
Kral

Re: relay voltage

Kral, I'll see if I can simplify this.
I have a monostable 555ic timer circuit. The timer gives me a 2.4 second on period when triggered.
I have 2 spdt 5v relays with the 2 coils connected parallel so the relays can be used for motor reversing.
The timer output is connected to the coils so that when the timer is triggered on, the coils are energized for 2.4 seconds.

If I use a 9v battery to power the timer (8v output on timer), when the timer is triggered, the relays latch on untill I trigger the timer again.

If I use 5v to power the timer (4v output on timer) the relays energize for 2.4 seconds then deenergize.

Why do the relays latch on at the higher voltage but not at the lower voltage?
Keep in mind that the relays are 5v relays.
If you still need schematics, I have the timer circuit that I got off the internet but will have to draw out the relay circuit.
Let me know if you need the schematics.
Thanks
Bill

Re: relay voltage

gnomeman,
The solution is not obvious to me. You mentioned that you are using a 9V battery as your high voltage source and obtained an 8V output. Was this the open circuit output, or the output with the relays energized. With an 8V source and two 59 Ohm relays as a load, the output current would be 271 mA. The 555 is not specified for output currents >200 mA. Have you monitored the battery voltage and output voltage while the relays are energized with the 9V battery supply?
Regards,
Kral

Re: relay voltage

Kral. No need to go into this further. I was just curiouse.
The voltages I mentioned were aproximat. The 8v output was no load.
Maybe the higher ma was affecting the 555 to the point that it latched instead of timing out. No, I did not monitor the voltage with the relays connected.
In any case, the timer and relays are working great with a 5v supply.
Tomorrow night I will post schematics of my circuits so you can see what I have done with them.
Basicly, it is an object detecting circuit for my robot. The robot will have feelers attached to lever switches. The lever switchs are connected to the trigger on the timer. The timer will energize the relays, reverse the drive motor and also run a motor with a wheel that turns 90 degrees to the drive wheels. When the 90 deg wheel spins, it will move the back of the robot and thus change the direction that the robot will move in forward motion. The 90 deg wheel does not spin when the robot is moving forward.
Thanks for the info.
Bill
P.S. I love messing with electronics but wish I knew more about it. Because of this board and the internet, I'm learning more and more.