SURF PI 555 QUESTION

[daverave]

i tried the non vco option.

[kt315]

do you make VCO rev or without VCO? did you set IC9 or not?

[daverave]

hi kt
pin 5 of IC8 has 0v when no coil connected....the threshold control has no control over this constant tone coming from the audio...im not sure if this tone is the threshold or some internal problem that is over riding the threshold tone ...i have tried both the auto tune on and off......this hammer head has been much frustration for me to get working.

[kt315]

what you have on IC8b input pin 5? did you set the switch AUTOTRACK or not? do you set the switch in open state or not?

[daverave]

ok will check that out...be nice to get the HH working as spent many hours on this and got nowhere.

i have now got the coil drive working but yet another problem with the hammer head with high frequency tone on the audio and no threshold working...this has been a head ache for me since building it over a year ago...just too complicated...never had these problems with surf pi.

[daverave]

ok will check that out...be nice to get the HH working as spent many hours on this and got nowhere.

[Qiaozhi]

i appreciate your advice George with the hammerhead design to get around the problem but ive had no luck even getting the coil drive to work on the hammerhead which i made over a year ago...similar problem excessive current being drawn and mosfet over heating...which is another one of my project problems maybe with the surf pi i will just have to be happy with 16v to the coil.

You've probably got mixed up with the various options on the HH. It can be a bit confusing which links to insert, and which to leave out.
For the transmitter, you only need to insert the link that connects the gate of Q3 to the junction of R8/R9.
The other link is only there if you want to experiment with active turn-off.

[Constantin]

By th way, the 555 can also be configured as a negative voltage generator instead of the ICL7660 or the LT1054.

Is necessary a particular frequency to avoid interference?

[daverave]

i appreciate your advice George with the hammerhead design to get around the problem but ive had no luck even getting the coil drive to work on the hammerhead which i made over a year ago...similar problem excessive current being drawn and mosfet over heating...which is another one of my project problems maybe with the surf pi i will just have to be happy with 16v to the coil.

[chemelec]

The LT1054L has an operating voltage range of 3.5V to 7.0V, and the LT1054 has a range of 3.5V to 15.0V.
Absolute maximum values in this case are 7.0V and 16.0V respectively.

Another Option: The ICL7662 is good up to 20 Volts.

[kt315]

you are right George, my mistaken. forgot in surf is P channel one in HH N channel mos-fet.

[Qiaozhi]

Qiaozhi, if you mean HH first revision so the 555 is running from batt directly. or... what HH revision you meant?

Have a look at the attached HH schematic (D1). The 555 is connected to -5D, and the coil is connected to -VB.

Of course, the HH uses +VB as ground, whereas the Surf-PI uses -VB as ground. Therefore, you'll need to swap the transistor polarities around in order to use a PMOS to switch the coil.

[junkhunter]

i tryed a voltage regulator project went crazy didnt work propley

[kt315]

Qiaozhi, if you mean HH first revision so the 555 is running from batt directly. or... what HH revision you meant?

[Qiaozhi]

Hi Qiaozhi

is there a way around this problem ????

Have a look at the Hammerhead schematic. The 555 timer is running from a 5V supply, and the MOSFET is connected to the battery.
Basically, you will need to add a transistor between the output of the 555 and the MOSFET to invert the signal, and also reconfigure the 555 to invert the On-OFF pulses to compensate.